21990605 has 32 divisors (see below), whose sum is σ = 34401024. Its totient is φ = 13095936.

The previous prime is 21990589. The next prime is 21990611. The reversal of 21990605 is 50609912.

It is not a de Polignac number, because 21990605 - 2⁴ = 21990589 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6314 + ... + 9156.

It is an arithmetic number, because the mean of its divisors is an integer number (1075032).

Almost surely, 2^21990605 is an apocalyptic number.

It is an amenable number.

21990605 is a deficient number, since it is larger than the sum of its proper divisors (12410419).

21990605 is a wasteful number, since it uses less digits than its factorization.

21990605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2885.

The product of its (nonzero) digits is 4860, while the sum is 32.

The square root of 21990605 is about 4689.4141425129. The cubic root of 21990605 is about 280.1640407811.

The spelling of 21990605 in words is "twenty-one million, nine hundred ninety thousand, six hundred five".