21531112051 has 4 divisors (see below), whose sum is σ = 22797648072. Its totient is φ = 20264576032.

The previous prime is 21531112033. The next prime is 21531112067. The reversal of 21531112051 is 15021113512.

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 21531112051 - 2¹³ = 21531103859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21531112021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 633267985 + ... + 633268018.

It is an arithmetic number, because the mean of its divisors is an integer number (5699412018).

Almost surely, 2^21531112051 is an apocalyptic number.

21531112051 is a deficient number, since it is larger than the sum of its proper divisors (1266536021).

21531112051 is a wasteful number, since it uses less digits than its factorization.

21531112051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1266536020.

The product of its (nonzero) digits is 300, while the sum is 22.

Adding to 21531112051 its reverse (15021113512), we get a palindrome (36552225563).

The spelling of 21531112051 in words is "twenty-one billion, five hundred thirty-one million, one hundred twelve thousand, fifty-one".