21153631 has 4 divisors (see below), whose sum is σ = 22267000. Its totient is φ = 20040264.

The previous prime is 21153623. The next prime is 21153637. The reversal of 21153631 is 13635112.

It is a happy number.

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 21153631 - 2³ = 21153623 is a prime.

It is a super-2 number, since 2×21153631² = 894952208968322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21153637) 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, 556656 + ... + 556693.

It is an arithmetic number, because the mean of its divisors is an integer number (5566750).

Almost surely, 2^21153631 is an apocalyptic number.

21153631 is a deficient number, since it is larger than the sum of its proper divisors (1113369).

21153631 is a wasteful number, since it uses less digits than its factorization.

21153631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1113368.

The product of its digits is 540, while the sum is 22.

The square root of 21153631 is about 4599.3076652905. The cubic root of 21153631 is about 276.5635713685.

Adding to 21153631 its reverse (13635112), we get a palindrome (34788743).

The spelling of 21153631 in words is "twenty-one million, one hundred fifty-three thousand, six hundred thirty-one".