21665105131 has 4 divisors (see below), whose sum is σ = 21666619000. Its totient is φ = 21663591264.

The previous prime is 21665105087. The next prime is 21665105149. The reversal of 21665105131 is 13150156612.

It is a happy number.

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 21665105131 - 2⁹ = 21665104619 is a prime.

It is a super-2 number, since 2×21665105131² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21665105093 and 21665105102.

It is not an unprimeable number, because it can be changed into a prime (21665105431) 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, 735261 + ... + 764158.

It is an arithmetic number, because the mean of its divisors is an integer number (5416654750).

Almost surely, 2^21665105131 is an apocalyptic number.

21665105131 is a deficient number, since it is larger than the sum of its proper divisors (1513869).

21665105131 is a wasteful number, since it uses less digits than its factorization.

21665105131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1513868.

The product of its (nonzero) digits is 5400, while the sum is 31.

The spelling of 21665105131 in words is "twenty-one billion, six hundred sixty-five million, one hundred five thousand, one hundred thirty-one".