21263985 has 32 divisors (see below), whose sum is σ = 39029760. Its totient is φ = 10972800.

The previous prime is 21263959. The next prime is 21263987. The reversal of 21263985 is 58936212.

21263985 is a `hidden beast` number, since 2 + 12 + 639 + 8 + 5 = 666.

It is not a de Polignac number, because 21263985 - 2⁸ = 21263729 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21263987) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1645 + ... + 6725.

It is an arithmetic number, because the mean of its divisors is an integer number (1219680).

Almost surely, 2^21263985 is an apocalyptic number.

It is an amenable number.

21263985 is a deficient number, since it is larger than the sum of its proper divisors (17765775).

21263985 is a wasteful number, since it uses less digits than its factorization.

21263985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5126 (or 5120 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 21263985 is about 4611.2888653824. The cubic root of 21263985 is about 277.0436619606.

The spelling of 21263985 in words is "twenty-one million, two hundred sixty-three thousand, nine hundred eighty-five".