21485681 has 16 divisors (see below), whose sum is σ = 25753728. Its totient is φ = 17539200.

The previous prime is 21485677. The next prime is 21485687. The reversal of 21485681 is 18658412.

It is not a de Polignac number, because 21485681 - 2² = 21485677 is a prime.

It is a super-2 number, since 2×21485681² = 923268976067522, which contains 22 as substring.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21485687) 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 15 ways as a sum of consecutive naturals, for example, 11471 + ... + 13211.

It is an arithmetic number, because the mean of its divisors is an integer number (1609608).

Almost surely, 2^21485681 is an apocalyptic number.

It is an amenable number.

21485681 is a deficient number, since it is larger than the sum of its proper divisors (4268047).

21485681 is a wasteful number, since it uses less digits than its factorization.

21485681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1832.

The product of its digits is 15360, while the sum is 35.

The square root of 21485681 is about 4635.2649330971. The cubic root of 21485681 is about 278.0031442116.

The spelling of 21485681 in words is "twenty-one million, four hundred eighty-five thousand, six hundred eighty-one".