20661266531 has 4 divisors (see below), whose sum is σ = 20668536792. Its totient is φ = 20653996272.

The previous prime is 20661266513. The next prime is 20661266567. The reversal of 20661266531 is 13566216602.

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 20661266531 - 2¹⁰ = 20661265507 is a prime.

It is a super-2 number, since 2×20661266531² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20661256531) 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, 3630866 + ... + 3636551.

It is an arithmetic number, because the mean of its divisors is an integer number (5167134198).

Almost surely, 2^20661266531 is an apocalyptic number.

20661266531 is a deficient number, since it is larger than the sum of its proper divisors (7270261).

20661266531 is an equidigital number, since it uses as much as digits as its factorization.

20661266531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7270260.

The product of its (nonzero) digits is 77760, while the sum is 38.

The spelling of 20661266531 in words is "twenty billion, six hundred sixty-one million, two hundred sixty-six thousand, five hundred thirty-one".