21591963 has 12 divisors (see below), whose sum is σ = 32544720. Its totient is φ = 13768656.

The previous prime is 21591959. The next prime is 21591991. The reversal of 21591963 is 36919512.

21591963 is a `hidden beast` number, since 2 + 1 + 591 + 9 + 63 = 666.

It is not a de Polignac number, because 21591963 - 2² = 21591959 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21598963) 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, 51948 + ... + 52361.

It is an arithmetic number, because the mean of its divisors is an integer number (2712060).

Almost surely, 2^21591963 is an apocalyptic number.

21591963 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21591963 is a deficient number, since it is larger than the sum of its proper divisors (10952757).

21591963 is a wasteful number, since it uses less digits than its factorization.

21591963 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104338 (or 104335 counting only the distinct ones).

The product of its digits is 14580, while the sum is 36.

The square root of 21591963 is about 4646.7152914720. The cubic root of 21591963 is about 278.4607845749.

The spelling of 21591963 in words is "twenty-one million, five hundred ninety-one thousand, nine hundred sixty-three".