21661877179 has 4 divisors (see below), whose sum is σ = 21690046840. Its totient is φ = 21633707520.

The previous prime is 21661877117. The next prime is 21661877197. The reversal of 21661877179 is 97177816612.

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 21661877179 - 2²¹ = 21659780027 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21661877579) 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, 14083677 + ... + 14085214.

It is an arithmetic number, because the mean of its divisors is an integer number (5422511710).

Almost surely, 2^21661877179 is an apocalyptic number.

21661877179 is a deficient number, since it is larger than the sum of its proper divisors (28169661).

21661877179 is an equidigital number, since it uses as much as digits as its factorization.

21661877179 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28169660.

The product of its digits is 1778112, while the sum is 55.

The spelling of 21661877179 in words is "twenty-one billion, six hundred sixty-one million, eight hundred seventy-seven thousand, one hundred seventy-nine".