391779964889981 has 2 divisors, whose sum is σ = 391779964889982. Its totient is φ = 391779964889980.

The previous prime is 391779964889953. The next prime is 391779964889987. The reversal of 391779964889981 is 189988469977193.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 347492137781881 + 44287827108100 = 18641141^2 + 6654910^2 .

It is a cyclic number.

It is not a de Polignac number, because 391779964889981 - 2¹⁰ = 391779964888957 is a prime.

It is a super-2 number, since 2×391779964889981² (a number of 30 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (391779964889987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195889982444990 + 195889982444991.

It is an arithmetic number, because the mean of its divisors is an integer number (195889982444991).

Almost surely, 2^{391779964889981} is an apocalyptic number.

It is an amenable number.

391779964889981 is a deficient number, since it is larger than the sum of its proper divisors (1).

391779964889981 is an equidigital number, since it uses as much as digits as its factorization.

391779964889981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 106662334464, while the sum is 98.

The spelling of 391779964889981 in words is "three hundred ninety-one trillion, seven hundred seventy-nine billion, nine hundred sixty-four million, eight hundred eighty-nine thousand, nine hundred eighty-one".