2021311681 has 3 divisors (see below), whose sum is σ = 2021356641. Its totient is φ = 2021266722.

The previous prime is 2021311667. The next prime is 2021311703. The reversal of 2021311681 is 1861131202.

The square root of 2021311681 is 44959.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a de Polignac number, because none of the positive numbers 2^k-2021311681 is a prime.

It is a super-2 number, since 2×2021311681² = 8171401823494091522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2021311601) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 22480 + ... + 67438.

It is an arithmetic number, because the mean of its divisors is an integer number (673785547).

Almost surely, 2^2021311681 is an apocalyptic number.

2021311681 is the 44959-th square number.

2021311681 is the 22480-th centered octagonal number.

It is an amenable number.

2021311681 is a deficient number, since it is larger than the sum of its proper divisors (44960).

2021311681 is an frugal number, since it uses more digits than its factorization.

2021311681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89918 (or 44959 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 25.

The cubic root of 2021311681 is about 1264.3804203403.

Multiplying 2021311681 by its sum of digits (25), we get a square (50532792025 = 224795²).

Multiplying 2021311681 by its product of nonzero digits (576), we get a square (1164275528256 = 1079016²).

Adding to 2021311681 its reverse (1861131202), we get a palindrome (3882442883).

The spelling of 2021311681 in words is "two billion, twenty-one million, three hundred eleven thousand, six hundred eighty-one".