21275173661 has 4 divisors (see below), whose sum is σ = 24314484192. Its totient is φ = 18235863132.

The previous prime is 21275173631. The next prime is 21275173681. The reversal of 21275173661 is 16637157212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21275173661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21275173631) 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, 1519655255 + ... + 1519655268.

It is an arithmetic number, because the mean of its divisors is an integer number (6078621048).

Almost surely, 2^21275173661 is an apocalyptic number.

It is an amenable number.

21275173661 is a deficient number, since it is larger than the sum of its proper divisors (3039310531).

21275173661 is an equidigital number, since it uses as much as digits as its factorization.

21275173661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3039310530.

The product of its digits is 105840, while the sum is 41.

The spelling of 21275173661 in words is "twenty-one billion, two hundred seventy-five million, one hundred seventy-three thousand, six hundred sixty-one".