21053681 has 16 divisors (see below), whose sum is σ = 24537600. Its totient is φ = 17875200.

The previous prime is 21053663. The next prime is 21053699. The reversal of 21053681 is 18635012.

It is an interprime number because it is at equal distance from previous prime (21053663) and next prime (21053699).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21053681 is a prime.

It is a super-2 number, since 2×21053681² = 886514967299522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21053681.

It is not an unprimeable number, because it can be changed into a prime (21053651) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8825 + ... + 10953.

It is an arithmetic number, because the mean of its divisors is an integer number (1533600).

Almost surely, 2^21053681 is an apocalyptic number.

It is an amenable number.

21053681 is a deficient number, since it is larger than the sum of its proper divisors (3483919).

21053681 is a wasteful number, since it uses less digits than its factorization.

21053681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2200.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21053681 is about 4588.4290339941. The cubic root of 21053681 is about 276.1272998494.

Adding to 21053681 its reverse (18635012), we get a palindrome (39688693).

The spelling of 21053681 in words is "twenty-one million, fifty-three thousand, six hundred eighty-one".