21508790 has 8 divisors (see below), whose sum is σ = 38715840. Its totient is φ = 8603512.

The previous prime is 21508789. The next prime is 21508801. The reversal of 21508790 is 9780512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1075430 + ... + 1075449.

It is an arithmetic number, because the mean of its divisors is an integer number (4839480).

Almost surely, 2^21508790 is an apocalyptic number.

21508790 is a deficient number, since it is larger than the sum of its proper divisors (17207050).

21508790 is a wasteful number, since it uses less digits than its factorization.

21508790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2150886.

The product of its (nonzero) digits is 5040, while the sum is 32.

The square root of 21508790 is about 4637.7570009650. The cubic root of 21508790 is about 278.1027775873.

The spelling of 21508790 in words is "twenty-one million, five hundred eight thousand, seven hundred ninety".