21621531 has 8 divisors (see below), whose sum is σ = 28877904. Its totient is φ = 14389760.

The previous prime is 21621527. The next prime is 21621547. The reversal of 21621531 is 13512612.

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 21621531 - 2² = 21621527 is a prime.

It is a super-2 number, since 2×21621531² = 934981205567922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21621498 and 21621507.

It is not an unprimeable number, because it can be changed into a prime (21621631) 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, 3990 + ... + 7691.

It is an arithmetic number, because the mean of its divisors is an integer number (3609738).

Almost surely, 2^21621531 is an apocalyptic number.

21621531 is a deficient number, since it is larger than the sum of its proper divisors (7256373).

21621531 is a wasteful number, since it uses less digits than its factorization.

21621531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12301.

The product of its digits is 360, while the sum is 21.

The square root of 21621531 is about 4649.8958052842. The cubic root of 21621531 is about 278.5878345180.

The spelling of 21621531 in words is "twenty-one million, six hundred twenty-one thousand, five hundred thirty-one".