21991776757 has 2 divisors, whose sum is σ = 21991776758. Its totient is φ = 21991776756.

The previous prime is 21991776739. The next prime is 21991776769. The reversal of 21991776757 is 75767719912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16985648241 + 5006128516 = 130329^2 + 70754^2 .

It is a cyclic number.

It is not a de Polignac number, because 21991776757 - 2¹⁹ = 21991252469 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21991776695 and 21991776704.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21991776787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10995888378 + 10995888379.

It is an arithmetic number, because the mean of its divisors is an integer number (10995888379).

Almost surely, 2^21991776757 is an apocalyptic number.

It is an amenable number.

21991776757 is a deficient number, since it is larger than the sum of its proper divisors (1).

21991776757 is an equidigital number, since it uses as much as digits as its factorization.

21991776757 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11668860, while the sum is 61.

The spelling of 21991776757 in words is "twenty-one billion, nine hundred ninety-one million, seven hundred seventy-six thousand, seven hundred fifty-seven".