21591625 has 32 divisors (see below), whose sum is σ = 30191616. Its totient is φ = 15280000.

The previous prime is 21591623. The next prime is 21591629. The reversal of 21591625 is 52619512.

It is not a de Polignac number, because 21591625 - 2¹ = 21591623 is a prime.

It is a Duffinian number.

Its product of digits (5400) is a multiple of the sum of its prime factors (450).

It is not an unprimeable number, because it can be changed into a prime (21591623) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 56184 + ... + 56566.

It is an arithmetic number, because the mean of its divisors is an integer number (943488).

Almost surely, 2^21591625 is an apocalyptic number.

21591625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21591625 is a deficient number, since it is larger than the sum of its proper divisors (8599991).

21591625 is a wasteful number, since it uses less digits than its factorization.

21591625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 450 (or 440 counting only the distinct ones).

The product of its digits is 5400, while the sum is 31.

The square root of 21591625 is about 4646.6789215525. The cubic root of 21591625 is about 278.4593315615.

The spelling of 21591625 in words is "twenty-one million, five hundred ninety-one thousand, six hundred twenty-five".