21671725 has 6 divisors (see below), whose sum is σ = 26872970. Its totient is φ = 17337360.

The previous prime is 21671701. The next prime is 21671731. The reversal of 21671725 is 52717612.

It can be written as a sum of positive squares in 3 ways, for example, as 21316 + 21650409 = 146^2 + 4653^2 .

It is not a de Polignac number, because 21671725 - 2⁷ = 21671597 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 433410 + ... + 433459.

Almost surely, 2^21671725 is an apocalyptic number.

21671725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21671725 is a deficient number, since it is larger than the sum of its proper divisors (5201245).

21671725 is an equidigital number, since it uses as much as digits as its factorization.

21671725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 866879 (or 866874 counting only the distinct ones).

The product of its digits is 5880, while the sum is 31.

The square root of 21671725 is about 4655.2900017077. The cubic root of 21671725 is about 278.8032468143.

The spelling of 21671725 in words is "twenty-one million, six hundred seventy-one thousand, seven hundred twenty-five".