21072681 has 12 divisors (see below), whose sum is σ = 34786752. Its totient is φ = 12041496.

The previous prime is 21072677. The next prime is 21072683. The reversal of 21072681 is 18627012.

It is not a de Polignac number, because 21072681 - 2² = 21072677 is a prime.

It is a super-2 number, since 2×21072681² = 888115769055522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21072683) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 167181 + ... + 167306.

It is an arithmetic number, because the mean of its divisors is an integer number (2898896).

Almost surely, 2^21072681 is an apocalyptic number.

21072681 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21072681 is a deficient number, since it is larger than the sum of its proper divisors (13714071).

21072681 is a wasteful number, since it uses less digits than its factorization.

21072681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334500 (or 334497 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21072681 is about 4590.4989924844. The cubic root of 21072681 is about 276.2103390302.

Adding to 21072681 its reverse (18627012), we get a palindrome (39699693).

The spelling of 21072681 in words is "twenty-one million, seventy-two thousand, six hundred eighty-one".