21861253 has 4 divisors (see below), whose sum is σ = 21894988. Its totient is φ = 21827520.

The previous prime is 21861239. The next prime is 21861263. The reversal of 21861253 is 35216812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14010049 + 7851204 = 3743^2 + 2802^2 .

It is a cyclic number.

It is not a de Polignac number, because 21861253 - 2⁵ = 21861221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21861233) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15876 + ... + 17197.

It is an arithmetic number, because the mean of its divisors is an integer number (5473747).

Almost surely, 2^21861253 is an apocalyptic number.

It is an amenable number.

21861253 is a deficient number, since it is larger than the sum of its proper divisors (33735).

21861253 is an equidigital number, since it uses as much as digits as its factorization.

21861253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33734.

The product of its digits is 2880, while the sum is 28.

The square root of 21861253 is about 4675.6018863885. The cubic root of 21861253 is about 279.6136380366.

The spelling of 21861253 in words is "twenty-one million, eight hundred sixty-one thousand, two hundred fifty-three".