971785511981 has 2 divisors, whose sum is σ = 971785511982. Its totient is φ = 971785511980.

The previous prime is 971785511959. The next prime is 971785512031. The reversal of 971785511981 is 189115587179.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 526155833956 + 445629678025 = 725366^2 + 667555^2 .

It is an emirp because it is prime and its reverse (189115587179) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-971785511981 is a prime.

It is a super-2 number, since 2×971785511981² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (971785511911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 485892755990 + 485892755991.

It is an arithmetic number, because the mean of its divisors is an integer number (485892755991).

Almost surely, 2^971785511981 is an apocalyptic number.

It is an amenable number.

971785511981 is a deficient number, since it is larger than the sum of its proper divisors (1).

971785511981 is an equidigital number, since it uses as much as digits as its factorization.

971785511981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6350400, while the sum is 62.

The spelling of 971785511981 in words is "nine hundred seventy-one billion, seven hundred eighty-five million, five hundred eleven thousand, nine hundred eighty-one".