21389725 has 36 divisors (see below), whose sum is σ = 32512800. Its totient is φ = 13880160.

The previous prime is 21389713. The next prime is 21389729. The reversal of 21389725 is 52798312.

It is a de Polignac number, because none of the positive numbers 2^k-21389725 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21389729) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 22816 + ... + 23734.

Almost surely, 2^21389725 is an apocalyptic number.

21389725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21389725 is a deficient number, since it is larger than the sum of its proper divisors (11123075).

21389725 is a wasteful number, since it uses less digits than its factorization.

21389725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 962 (or 950 counting only the distinct ones).

The product of its digits is 30240, while the sum is 37.

The square root of 21389725 is about 4624.9027016792. The cubic root of 21389725 is about 277.5886684700.

The spelling of 21389725 in words is "twenty-one million, three hundred eighty-nine thousand, seven hundred twenty-five".