21370925 has 18 divisors (see below), whose sum is σ = 27214218. Its totient is φ = 16642080.

The previous prime is 21370913. The next prime is 21370927. The reversal of 21370925 is 52907312.

It can be written as a sum of positive squares in 3 ways, for example, as 2725801 + 18645124 = 1651^2 + 4318^2 .

It is not a de Polignac number, because 21370925 - 2²⁴ = 4593709 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21370927) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 168212 + ... + 168338.

It is an arithmetic number, because the mean of its divisors is an integer number (1511901).

Almost surely, 2^21370925 is an apocalyptic number.

21370925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21370925 is a deficient number, since it is larger than the sum of its proper divisors (5843293).

21370925 is an equidigital number, since it uses as much as digits as its factorization.

21370925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 317 (or 185 counting only the distinct ones).

The product of its (nonzero) digits is 3780, while the sum is 29.

The square root of 21370925 is about 4622.8697796931. The cubic root of 21370925 is about 277.5073179360.

The spelling of 21370925 in words is "twenty-one million, three hundred seventy thousand, nine hundred twenty-five".