21724625 has 32 divisors (see below), whose sum is σ = 30270240. Its totient is φ = 15456000.

The previous prime is 21724621. The next prime is 21724649. The reversal of 21724625 is 52642712.

It is a happy number.

It can be written as a sum of positive squares in 16 ways, for example, as 19855936 + 1868689 = 4456^2 + 1367^2 .

It is not a de Polignac number, because 21724625 - 2² = 21724621 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is not an unprimeable number, because it can be changed into a prime (21724621) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 46895 + ... + 47355.

It is an arithmetic number, because the mean of its divisors is an integer number (945945).

Almost surely, 2^21724625 is an apocalyptic number.

21724625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21724625 is a deficient number, since it is larger than the sum of its proper divisors (8545615).

21724625 is a wasteful number, since it uses less digits than its factorization.

21724625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 518 (or 508 counting only the distinct ones).

The product of its digits is 6720, while the sum is 29.

The square root of 21724625 is about 4660.9682470491. The cubic root of 21724625 is about 279.0299124757.

It can be divided in two parts, 217 and 24625, that added together give a palindrome (24842).

The spelling of 21724625 in words is "twenty-one million, seven hundred twenty-four thousand, six hundred twenty-five".