20201981 has 6 divisors (see below), whose sum is σ = 21119070. Its totient is φ = 19323128.

The previous prime is 20201969. The next prime is 20201983. The reversal of 20201981 is 18910202.

It can be written as a sum of positive squares in only one way, i.e., 13205956 + 6996025 = 3634^2 + 2645^2 .

It is not a de Polignac number, because 20201981 - 2⁶ = 20201917 is a prime.

It is a super-2 number, since 2×20201981² = 816240072648722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20201983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 18566 + ... + 19623.

It is an arithmetic number, because the mean of its divisors is an integer number (3519845).

Almost surely, 2^20201981 is an apocalyptic number.

It is an amenable number.

20201981 is a deficient number, since it is larger than the sum of its proper divisors (917089).

20201981 is an equidigital number, since it uses as much as digits as its factorization.

20201981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38235 (or 38212 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 20201981 is about 4494.6613888034. The cubic root of 20201981 is about 272.3524707142.

The spelling of 20201981 in words is "twenty million, two hundred one thousand, nine hundred eighty-one".