21656253 has 8 divisors (see below), whose sum is σ = 29270848. Its totient is φ = 14239584.

The previous prime is 21656251. The next prime is 21656263. The reversal of 21656253 is 35265612.

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

It is not a de Polignac number, because 21656253 - 2¹ = 21656251 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21656253.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656251) 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, 49225 + ... + 49662.

It is an arithmetic number, because the mean of its divisors is an integer number (3658856).

Almost surely, 2^21656253 is an apocalyptic number.

It is an amenable number.

21656253 is a deficient number, since it is larger than the sum of its proper divisors (7614595).

21656253 is an equidigital number, since it uses as much as digits as its factorization.

21656253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98963.

The product of its digits is 10800, while the sum is 30.

The square root of 21656253 is about 4653.6279395757. The cubic root of 21656253 is about 278.7368827573.

The spelling of 21656253 in words is "twenty-one million, six hundred fifty-six thousand, two hundred fifty-three".