21979642779949 has 2 divisors, whose sum is σ = 21979642779950. Its totient is φ = 21979642779948.

The previous prime is 21979642779847. The next prime is 21979642779953. The reversal of 21979642779949 is 94997724697912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12051881582724 + 9927761197225 = 3471582^2 + 3150835^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21979642779949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21979642779989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10989821389974 + 10989821389975.

It is an arithmetic number, because the mean of its divisors is an integer number (10989821389975).

Almost surely, 2^{21979642779949} is an apocalyptic number.

It is an amenable number.

21979642779949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21979642779949 is an equidigital number, since it uses as much as digits as its factorization.

21979642779949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7777461888, while the sum is 85.

The spelling of 21979642779949 in words is "twenty-one trillion, nine hundred seventy-nine billion, six hundred forty-two million, seven hundred seventy-nine thousand, nine hundred forty-nine".