21668725 has 24 divisors (see below), whose sum is σ = 29437352. Its totient is φ = 15724800.

The previous prime is 21668723. The next prime is 21668729. The reversal of 21668725 is 52786612.

It is a happy number.

It can be written as a sum of positive squares in 12 ways, for example, as 8988004 + 12680721 = 2998^2 + 3561^2 .

It is not a de Polignac number, because 21668725 - 2¹ = 21668723 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19279 + ... + 20371.

Almost surely, 2^21668725 is an apocalyptic number.

21668725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21668725 is a deficient number, since it is larger than the sum of its proper divisors (7768627).

21668725 is a wasteful number, since it uses less digits than its factorization.

21668725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1177 (or 1172 counting only the distinct ones).

The product of its digits is 40320, while the sum is 37.

The square root of 21668725 is about 4654.9677764728. The cubic root of 21668725 is about 278.7903813820.

It can be divided in two parts, 21 and 668725, that added together give a triangular number (668746 = T₁₁₅₆).

The spelling of 21668725 in words is "twenty-one million, six hundred sixty-eight thousand, seven hundred twenty-five".