21853251 has 12 divisors (see below), whose sum is σ = 36075312. Its totient is φ = 12487536.

The previous prime is 21853231. The next prime is 21853309. The reversal of 21853251 is 15235812.

It is a happy number.

It is not a de Polignac number, because 21853251 - 2⁵ = 21853219 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21853231) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 173376 + ... + 173501.

It is an arithmetic number, because the mean of its divisors is an integer number (3006276).

Almost surely, 2^21853251 is an apocalyptic number.

21853251 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21853251 is a deficient number, since it is larger than the sum of its proper divisors (14222061).

21853251 is a wasteful number, since it uses less digits than its factorization.

21853251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 346890 (or 346887 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 21853251 is about 4674.7460893614. The cubic root of 21853251 is about 279.5795176778.

The spelling of 21853251 in words is "twenty-one million, eight hundred fifty-three thousand, two hundred fifty-one".