21625491 has 16 divisors (see below), whose sum is σ = 29826720. Its totient is φ = 13927680.

The previous prime is 21625489. The next prime is 21625531. The reversal of 21625491 is 19452612.

It is not a de Polignac number, because 21625491 - 2¹ = 21625489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21625091) 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, 12601 + ... + 14213.

It is an arithmetic number, because the mean of its divisors is an integer number (1864170).

Almost surely, 2^21625491 is an apocalyptic number.

21625491 is a deficient number, since it is larger than the sum of its proper divisors (8201229).

21625491 is a wasteful number, since it uses less digits than its factorization.

21625491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1766.

The product of its digits is 4320, while the sum is 30.

The square root of 21625491 is about 4650.3216017820. The cubic root of 21625491 is about 278.6048413383.

The spelling of 21625491 in words is "twenty-one million, six hundred twenty-five thousand, four hundred ninety-one".