21779617 has 4 divisors (see below), whose sum is σ = 21979540. Its totient is φ = 21579696.

The previous prime is 21779599. The next prime is 21779621. The reversal of 21779617 is 71697712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19927296 + 1852321 = 4464^2 + 1361^2 .

It is a cyclic number.

It is not a de Polignac number, because 21779617 - 2¹⁹ = 21255329 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21779617.

It is not an unprimeable number, because it can be changed into a prime (21779627) 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, 99798 + ... + 100015.

It is an arithmetic number, because the mean of its divisors is an integer number (5494885).

Almost surely, 2^21779617 is an apocalyptic number.

It is an amenable number.

21779617 is a deficient number, since it is larger than the sum of its proper divisors (199923).

21779617 is a wasteful number, since it uses less digits than its factorization.

21779617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199922.

The product of its digits is 37044, while the sum is 40.

The square root of 21779617 is about 4666.8637220300. The cubic root of 21779617 is about 279.2651521927.

The spelling of 21779617 in words is "twenty-one million, seven hundred seventy-nine thousand, six hundred seventeen".