21085590 has 16 divisors (see below), whose sum is σ = 50605488. Its totient is φ = 5622816.

The previous prime is 21085583. The next prime is 21085591. The reversal of 21085590 is 9558012.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 702853 = 21085590 / (2 + 1 + 0 + 8 + 5 + 5 + 9 + 0).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21085591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 351397 + ... + 351456.

It is an arithmetic number, because the mean of its divisors is an integer number (3162843).

Almost surely, 2^21085590 is an apocalyptic number.

21085590 is an abundant number, since it is smaller than the sum of its proper divisors (29519898).

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

21085590 is a wasteful number, since it uses less digits than its factorization.

21085590 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 702863.

The product of its (nonzero) digits is 3600, while the sum is 30.

The square root of 21085590 is about 4591.9048335086. The cubic root of 21085590 is about 276.2667291248.

The spelling of 21085590 in words is "twenty-one million, eighty-five thousand, five hundred ninety".