21121534531 has 4 divisors (see below), whose sum is σ = 21122118864. Its totient is φ = 21120950200.

The previous prime is 21121534523. The next prime is 21121534537. The reversal of 21121534531 is 13543512112.

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 21121534531 - 2³ = 21121534523 is a prime.

It is a super-2 number, since 2×21121534531² (a number of 21 digits) 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 21121534531.

It is not an unprimeable number, because it can be changed into a prime (21121534537) 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, 234100 + ... + 311521.

It is an arithmetic number, because the mean of its divisors is an integer number (5280529716).

Almost surely, 2^21121534531 is an apocalyptic number.

21121534531 is a deficient number, since it is larger than the sum of its proper divisors (584333).

21121534531 is an equidigital number, since it uses as much as digits as its factorization.

21121534531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 584332.

The product of its digits is 3600, while the sum is 28.

The spelling of 21121534531 in words is "twenty-one billion, one hundred twenty-one million, five hundred thirty-four thousand, five hundred thirty-one".