21966779 has 4 divisors (see below), whose sum is σ = 22172184. Its totient is φ = 21761376.

The previous prime is 21966773. The next prime is 21966781. The reversal of 21966779 is 97766912.

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 21966779 - 2¹² = 21962683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21966773) 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, 102542 + ... + 102755.

It is an arithmetic number, because the mean of its divisors is an integer number (5543046).

Almost surely, 2^21966779 is an apocalyptic number.

21966779 is a deficient number, since it is larger than the sum of its proper divisors (205405).

21966779 is a wasteful number, since it uses less digits than its factorization.

21966779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205404.

The product of its digits is 285768, while the sum is 47.

The square root of 21966779 is about 4686.8730514064. The cubic root of 21966779 is about 280.0628217884.

The spelling of 21966779 in words is "twenty-one million, nine hundred sixty-six thousand, seven hundred seventy-nine".