21857525 has 6 divisors (see below), whose sum is σ = 27103362. Its totient is φ = 17486000.

The previous prime is 21857519. The next prime is 21857533. The reversal of 21857525 is 52575812.

It can be written as a sum of positive squares in 3 ways, for example, as 2900209 + 18957316 = 1703^2 + 4354^2 .

It is not a de Polignac number, because 21857525 - 2¹⁶ = 21791989 is a prime.

It is a Duffinian number.

It is a congruent number.

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 5 ways as a sum of consecutive naturals, for example, 437126 + ... + 437175.

It is an arithmetic number, because the mean of its divisors is an integer number (4517227).

Almost surely, 2^21857525 is an apocalyptic number.

21857525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21857525 is a deficient number, since it is larger than the sum of its proper divisors (5245837).

21857525 is an equidigital number, since it uses as much as digits as its factorization.

21857525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 874311 (or 874306 counting only the distinct ones).

The product of its digits is 28000, while the sum is 35.

The square root of 21857525 is about 4675.2032041399. The cubic root of 21857525 is about 279.5977429595.

The spelling of 21857525 in words is "twenty-one million, eight hundred fifty-seven thousand, five hundred twenty-five".