21555653 has 4 divisors (see below), whose sum is σ = 24635040. Its totient is φ = 18476268.

The previous prime is 21555647. The next prime is 21555673. The reversal of 21555653 is 35655512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21555653 - 2⁴ = 21555637 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 (21555673) 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, 1539683 + ... + 1539696.

It is an arithmetic number, because the mean of its divisors is an integer number (6158760).

Almost surely, 2^21555653 is an apocalyptic number.

It is an amenable number.

21555653 is a deficient number, since it is larger than the sum of its proper divisors (3079387).

21555653 is an equidigital number, since it uses as much as digits as its factorization.

21555653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3079386.

The product of its digits is 22500, while the sum is 32.

The square root of 21555653 is about 4642.8065865379. The cubic root of 21555653 is about 278.3046063395.

The spelling of 21555653 in words is "twenty-one million, five hundred fifty-five thousand, six hundred fifty-three".