21553631 has 4 divisors (see below), whose sum is σ = 23513064. Its totient is φ = 19594200.

The previous prime is 21553627. The next prime is 21553633. The reversal of 21553631 is 13635512.

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

It is a cyclic number.

It is not a de Polignac number, because 21553631 - 2² = 21553627 is a prime.

It is a super-2 number, since 2×21553631² = 929118018568322, which contains 22 as substring.

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 21553631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553633) 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, 979700 + ... + 979721.

It is an arithmetic number, because the mean of its divisors is an integer number (5878266).

Almost surely, 2^21553631 is an apocalyptic number.

21553631 is a deficient number, since it is larger than the sum of its proper divisors (1959433).

21553631 is a wasteful number, since it uses less digits than its factorization.

21553631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1959432.

The product of its digits is 2700, while the sum is 26.

The square root of 21553631 is about 4642.5888252138. The cubic root of 21553631 is about 278.2959040668.

The spelling of 21553631 in words is "twenty-one million, five hundred fifty-three thousand, six hundred thirty-one".