21407725 has 6 divisors (see below), whose sum is σ = 26545610. Its totient is φ = 17126160.

The previous prime is 21407717. The next prime is 21407783. The reversal of 21407725 is 52770412.

It can be written as a sum of positive squares in 3 ways, for example, as 586756 + 20820969 = 766^2 + 4563^2 .

It is not a de Polignac number, because 21407725 - 2³ = 21407717 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21407693 and 21407702.

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, 428130 + ... + 428179.

Almost surely, 2^21407725 is an apocalyptic number.

21407725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21407725 is a deficient number, since it is larger than the sum of its proper divisors (5137885).

21407725 is an equidigital number, since it uses as much as digits as its factorization.

21407725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 856319 (or 856314 counting only the distinct ones).

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 21407725 is about 4626.8482793366. The cubic root of 21407725 is about 277.6665126234. Note that the first 3 decimals are identical.

The spelling of 21407725 in words is "twenty-one million, four hundred seven thousand, seven hundred twenty-five".