21500725 has 6 divisors (see below), whose sum is σ = 26660930. Its totient is φ = 17200560.

The previous prime is 21500711. The next prime is 21500741. The reversal of 21500725 is 52700512.

It can be written as a sum of positive squares in 3 ways, for example, as 5803281 + 15697444 = 2409^2 + 3962^2 .

It is not a de Polignac number, because 21500725 - 2¹³ = 21492533 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21500696 and 21500705.

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, 429990 + ... + 430039.

Almost surely, 2^21500725 is an apocalyptic number.

21500725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21500725 is a deficient number, since it is larger than the sum of its proper divisors (5160205).

21500725 is an equidigital number, since it uses as much as digits as its factorization.

21500725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 860039 (or 860034 counting only the distinct ones).

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 21500725 is about 4636.8874258494. The cubic root of 21500725 is about 278.0680138265.

The spelling of 21500725 in words is "twenty-one million, five hundred thousand, seven hundred twenty-five".