21065105631 has 4 divisors (see below), whose sum is σ = 28086807512. Its totient is φ = 14043403752.

The previous prime is 21065105629. The next prime is 21065105683. The reversal of 21065105631 is 13650156012.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21065105631 - 2¹ = 21065105629 is a prime.

It is a super-2 number, since 2×21065105631² (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 (21065105431) 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, 3510850936 + ... + 3510850941.

It is an arithmetic number, because the mean of its divisors is an integer number (7021701878).

Almost surely, 2^21065105631 is an apocalyptic number.

21065105631 is a deficient number, since it is larger than the sum of its proper divisors (7021701881).

21065105631 is an equidigital number, since it uses as much as digits as its factorization.

21065105631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7021701880.

The product of its (nonzero) digits is 5400, while the sum is 30.

The spelling of 21065105631 in words is "twenty-one billion, sixty-five million, one hundred five thousand, six hundred thirty-one".