21708725 has 6 divisors (see below), whose sum is σ = 26918850. Its totient is φ = 17366960.

The previous prime is 21708703. The next prime is 21708727. The reversal of 21708725 is 52780712.

It can be written as a sum of positive squares in 3 ways, for example, as 244036 + 21464689 = 494^2 + 4633^2 .

It is not a de Polignac number, because 21708725 - 2¹⁰ = 21707701 is a prime.

It is a super-2 number, since 2×21708725² = 942537482251250, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21708691 and 21708700.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21708727) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 434150 + ... + 434199.

It is an arithmetic number, because the mean of its divisors is an integer number (4486475).

Almost surely, 2^21708725 is an apocalyptic number.

21708725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21708725 is a deficient number, since it is larger than the sum of its proper divisors (5210125).

21708725 is an equidigital number, since it uses as much as digits as its factorization.

21708725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 868359 (or 868354 counting only the distinct ones).

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 21708725 is about 4659.2622806620. The cubic root of 21708725 is about 278.9618229474.

The spelling of 21708725 in words is "twenty-one million, seven hundred eight thousand, seven hundred twenty-five".