21513390 has 16 divisors (see below), whose sum is σ = 51632208. Its totient is φ = 5736896.

The previous prime is 21513383. The next prime is 21513403. The reversal of 21513390 is 9331512.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21513390.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 358527 + ... + 358586.

It is an arithmetic number, because the mean of its divisors is an integer number (3227013).

Almost surely, 2^21513390 is an apocalyptic number.

21513390 is an abundant number, since it is smaller than the sum of its proper divisors (30118818).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21513390 is a wasteful number, since it uses less digits than its factorization.

21513390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 717123.

The product of its (nonzero) digits is 810, while the sum is 24.

The square root of 21513390 is about 4638.2529038421. The cubic root of 21513390 is about 278.1226017552.

The spelling of 21513390 in words is "twenty-one million, five hundred thirteen thousand, three hundred ninety".