21138569779 has 2 divisors, whose sum is σ = 21138569780. Its totient is φ = 21138569778.

The previous prime is 21138569723. The next prime is 21138569801. The reversal of 21138569779 is 97796583112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21138569779 - 2²⁷ = 21004352051 is a prime.

It is not a weakly prime, because it can be changed into another prime (21138569279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569284889 + 10569284890.

It is an arithmetic number, because the mean of its divisors is an integer number (10569284890).

Almost surely, 2^21138569779 is an apocalyptic number.

21138569779 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138569779 is an equidigital number, since it uses as much as digits as its factorization.

21138569779 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5715360, while the sum is 58.

The spelling of 21138569779 in words is "twenty-one billion, one hundred thirty-eight million, five hundred sixty-nine thousand, seven hundred seventy-nine".