21261625 has 48 divisors (see below), whose sum is σ = 33800832. Its totient is φ = 12972000.

The previous prime is 21261623. The next prime is 21261631. The reversal of 21261625 is 52616212.

It is not a de Polignac number, because 21261625 - 2¹ = 21261623 is a prime.

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21261625.

It is not an unprimeable number, because it can be changed into a prime (21261623) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 452352 + ... + 452398.

It is an arithmetic number, because the mean of its divisors is an integer number (704184).

Almost surely, 2^21261625 is an apocalyptic number.

21261625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21261625 is a deficient number, since it is larger than the sum of its proper divisors (12539207).

21261625 is an equidigital number, since it uses as much as digits as its factorization.

21261625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127 (or 70 counting only the distinct ones).

The product of its digits is 1440, while the sum is 25.

The square root of 21261625 is about 4611.0329645319. The cubic root of 21261625 is about 277.0334122789.

Adding to 21261625 its reverse (52616212), we get a palindrome (73877837).

The spelling of 21261625 in words is "twenty-one million, two hundred sixty-one thousand, six hundred twenty-five".