21097578 has 48 divisors (see below), whose sum is σ = 46860480. Its totient is φ = 6331072.

The previous prime is 21097567. The next prime is 21097603. The reversal of 21097578 is 87579012.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 917275 + ... + 917297.

It is an arithmetic number, because the mean of its divisors is an integer number (976260).

Almost surely, 2^21097578 is an apocalyptic number.

21097578 is an abundant number, since it is smaller than the sum of its proper divisors (25762902).

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

21097578 is an equidigital number, since it uses as much as digits as its factorization.

21097578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108 (or 45 counting only the distinct ones).

The product of its (nonzero) digits is 35280, while the sum is 39.

The square root of 21097578 is about 4593.2099886681. The cubic root of 21097578 is about 276.3190754286.

The spelling of 21097578 in words is "twenty-one million, ninety-seven thousand, five hundred seventy-eight".