21918625 has 8 divisors (see below), whose sum is σ = 27354600. Its totient is φ = 17534800.

The previous prime is 21918607. The next prime is 21918649. The reversal of 21918625 is 52681912.

It can be written as a sum of positive squares in 4 ways, for example, as 314721 + 21603904 = 561^2 + 4648^2 .

It is not a de Polignac number, because 21918625 - 2¹¹ = 21916577 is a prime.

It is a super-2 number, since 2×21918625² = 960852243781250, which contains 22 as substring.

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 87550 + ... + 87799.

It is an arithmetic number, because the mean of its divisors is an integer number (3419325).

Almost surely, 2^21918625 is an apocalyptic number.

21918625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21918625 is a deficient number, since it is larger than the sum of its proper divisors (5435975).

21918625 is an equidigital number, since it uses as much as digits as its factorization.

21918625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 175364 (or 175354 counting only the distinct ones).

The product of its digits is 8640, while the sum is 34.

The square root of 21918625 is about 4681.7331192626. The cubic root of 21918625 is about 279.8580275156.

It can be divided in two parts, 2191 and 8625, that added together give a square (10816 = 104²).

The spelling of 21918625 in words is "twenty-one million, nine hundred eighteen thousand, six hundred twenty-five".