21990356 has 12 divisors (see below), whose sum is σ = 38760960. Its totient is φ = 10915800.

The previous prime is 21990349. The next prime is 21990373. The reversal of 21990356 is 65309912.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19220 + ... + 20331.

It is an arithmetic number, because the mean of its divisors is an integer number (3230080).

Almost surely, 2^21990356 is an apocalyptic number.

It is an amenable number.

21990356 is a deficient number, since it is larger than the sum of its proper divisors (16770604).

21990356 is a wasteful number, since it uses less digits than its factorization.

21990356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39694 (or 39692 counting only the distinct ones).

The product of its (nonzero) digits is 14580, while the sum is 35.

The square root of 21990356 is about 4689.3875932791. The cubic root of 21990356 is about 280.1629833430.

The spelling of 21990356 in words is "twenty-one million, nine hundred ninety thousand, three hundred fifty-six".