21865253 has 8 divisors (see below), whose sum is σ = 22271040. Its totient is φ = 21463200.

The previous prime is 21865243. The next prime is 21865279. The reversal of 21865253 is 35256812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21865253 - 2⁴ = 21865237 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21865243) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12626 + ... + 14252.

It is an arithmetic number, because the mean of its divisors is an integer number (2783880).

Almost surely, 2^21865253 is an apocalyptic number.

It is an amenable number.

21865253 is a deficient number, since it is larger than the sum of its proper divisors (405787).

21865253 is a wasteful number, since it uses less digits than its factorization.

21865253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1867.

The product of its digits is 14400, while the sum is 32.

The square root of 21865253 is about 4676.0296192390. The cubic root of 21865253 is about 279.6306908307.

The spelling of 21865253 in words is "twenty-one million, eight hundred sixty-five thousand, two hundred fifty-three".