21770779957 has 2 divisors, whose sum is σ = 21770779958. Its totient is φ = 21770779956.

The previous prime is 21770779939. The next prime is 21770779967. The reversal of 21770779957 is 75997707712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20393553636 + 1377226321 = 142806^2 + 37111^2 .

It is a cyclic number.

It is not a de Polignac number, because 21770779957 - 2¹¹ = 21770777909 is a prime.

It is a super-2 number, since 2×21770779957² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21770779895 and 21770779904.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21770779967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10885389978 + 10885389979.

It is an arithmetic number, because the mean of its divisors is an integer number (10885389979).

Almost surely, 2^21770779957 is an apocalyptic number.

It is an amenable number.

21770779957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21770779957 is an equidigital number, since it uses as much as digits as its factorization.

21770779957 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13613670, while the sum is 61.

The spelling of 21770779957 in words is "twenty-one billion, seven hundred seventy million, seven hundred seventy-nine thousand, nine hundred fifty-seven".