21885251 has 4 divisors (see below), whose sum is σ = 21895272. Its totient is φ = 21875232.

The previous prime is 21885229. The next prime is 21885257. The reversal of 21885251 is 15258812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21885251 - 2⁶ = 21885187 is a prime.

It is a super-2 number, since 2×21885251² = 957928422666002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21885257) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 185 + ... + 6618.

It is an arithmetic number, because the mean of its divisors is an integer number (5473818).

Almost surely, 2^21885251 is an apocalyptic number.

21885251 is a deficient number, since it is larger than the sum of its proper divisors (10021).

21885251 is an equidigital number, since it uses as much as digits as its factorization.

21885251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10020.

The product of its digits is 6400, while the sum is 32.

The square root of 21885251 is about 4678.1674831070. The cubic root of 21885251 is about 279.7159150994.

The spelling of 21885251 in words is "twenty-one million, eight hundred eighty-five thousand, two hundred fifty-one".