21520388 has 12 divisors (see below), whose sum is σ = 39642960. Its totient is φ = 10193832.

The previous prime is 21520363. The next prime is 21520391. The reversal of 21520388 is 88302512.

It is a self number, because there is not a number n which added to its sum of digits gives 21520388.

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, 141506 + ... + 141657.

It is an arithmetic number, because the mean of its divisors is an integer number (3303580).

Almost surely, 2^21520388 is an apocalyptic number.

It is an amenable number.

21520388 is a deficient number, since it is larger than the sum of its proper divisors (18122572).

21520388 is a wasteful number, since it uses less digits than its factorization.

21520388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 283186 (or 283184 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 21520388 is about 4639.0072213783. The cubic root of 21520388 is about 278.1527549291.

The spelling of 21520388 in words is "twenty-one million, five hundred twenty thousand, three hundred eighty-eight".