21347531 has 4 divisors (see below), whose sum is σ = 21360864. Its totient is φ = 21334200.

The previous prime is 21347467. The next prime is 21347533. The reversal of 21347531 is 13574312.

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 21347531 - 2⁶ = 21347467 is a prime.

It is a super-2 number, since 2×21347531² = 911434159591922, 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 21347531.

It is not an unprimeable number, because it can be changed into a prime (21347533) 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, 3875 + ... + 7596.

It is an arithmetic number, because the mean of its divisors is an integer number (5340216).

Almost surely, 2^21347531 is an apocalyptic number.

21347531 is a deficient number, since it is larger than the sum of its proper divisors (13333).

21347531 is a wasteful number, since it uses less digits than its factorization.

21347531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13332.

The product of its digits is 2520, while the sum is 26.

The square root of 21347531 is about 4620.3388403882. The cubic root of 21347531 is about 277.4060217981.

The spelling of 21347531 in words is "twenty-one million, three hundred forty-seven thousand, five hundred thirty-one".