20656421531 has 4 divisors (see below), whose sum is σ = 21214703232. Its totient is φ = 20098139832.

The previous prime is 20656421497. The next prime is 20656421543. The reversal of 20656421531 is 13512465602.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20656421531 is a prime.

It is a super-2 number, since 2×20656421531² (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 = 20656421491 and 20656421500.

It is not an unprimeable number, because it can be changed into a prime (20656421231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 279140795 + ... + 279140868.

It is an arithmetic number, because the mean of its divisors is an integer number (5303675808).

Almost surely, 2^20656421531 is an apocalyptic number.

20656421531 is a deficient number, since it is larger than the sum of its proper divisors (558281701).

20656421531 is an equidigital number, since it uses as much as digits as its factorization.

20656421531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 558281700.

The product of its (nonzero) digits is 43200, while the sum is 35.

The spelling of 20656421531 in words is "twenty billion, six hundred fifty-six million, four hundred twenty-one thousand, five hundred thirty-one".