21138880831 has 4 divisors (see below), whose sum is σ = 21166228152. Its totient is φ = 21111533512.

The previous prime is 21138880817. The next prime is 21138880837. The reversal of 21138880831 is 13808883112.

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 21138880831 - 2⁵ = 21138880799 is a prime.

It is a super-2 number, since 2×21138880831² (a number of 21 digits) 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 (21138880837) 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, 13672501 + ... + 13674046.

It is an arithmetic number, because the mean of its divisors is an integer number (5291557038).

Almost surely, 2^21138880831 is an apocalyptic number.

21138880831 is a deficient number, since it is larger than the sum of its proper divisors (27347321).

21138880831 is an equidigital number, since it uses as much as digits as its factorization.

21138880831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27347320.

The product of its (nonzero) digits is 73728, while the sum is 43.

The spelling of 21138880831 in words is "twenty-one billion, one hundred thirty-eight million, eight hundred eighty thousand, eight hundred thirty-one".