21053881 has 6 divisors (see below), whose sum is σ = 22220682. Its totient is φ = 19945440.

The previous prime is 21053873. The next prime is 21053887. The reversal of 21053881 is 18835012.

It can be written as a sum of positive squares in only one way, i.e., 11696400 + 9357481 = 3420^2 + 3059^2 .

It is not a de Polignac number, because 21053881 - 2³ = 21053873 is a prime.

It is a super-2 number, since 2×21053881² = 886531810324322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21053887) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 28800 + ... + 29521.

It is an arithmetic number, because the mean of its divisors is an integer number (3703447).

Almost surely, 2^21053881 is an apocalyptic number.

It is an amenable number.

21053881 is a deficient number, since it is larger than the sum of its proper divisors (1166801).

21053881 is an equidigital number, since it uses as much as digits as its factorization.

21053881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58359 (or 58340 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 21053881 is about 4588.4508278939. The cubic root of 21053881 is about 276.1281742062.

Adding to 21053881 its reverse (18835012), we get a palindrome (39888893).

The spelling of 21053881 in words is "twenty-one million, fifty-three thousand, eight hundred eighty-one".