21578725 has 12 divisors (see below), whose sum is σ = 30580384. Its totient is φ = 14796720.

The previous prime is 21578681. The next prime is 21578731. The reversal of 21578725 is 52787512.

It is not a de Polignac number, because 21578725 - 2⁷ = 21578597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 61479 + ... + 61828.

Almost surely, 2^21578725 is an apocalyptic number.

21578725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21578725 is a deficient number, since it is larger than the sum of its proper divisors (9001659).

21578725 is a wasteful number, since it uses less digits than its factorization.

21578725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123324 (or 123319 counting only the distinct ones).

The product of its digits is 39200, while the sum is 37.

The square root of 21578725 is about 4645.2906259996. The cubic root of 21578725 is about 278.4038649783.

The spelling of 21578725 in words is "twenty-one million, five hundred seventy-eight thousand, seven hundred twenty-five".