97811991 has 12 divisors (see below), whose sum is σ = 141595168. Its totient is φ = 65064384.

The previous prime is 97811969. The next prime is 97812007. The reversal of 97811991 is 19911879.

It is not a de Polignac number, because 97811991 - 2¹³ = 97803799 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (97811921) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7570 + ... + 15903.

Almost surely, 2^97811991 is an apocalyptic number.

97811991 is a deficient number, since it is larger than the sum of its proper divisors (43783177).

97811991 is a wasteful number, since it uses less digits than its factorization.

97811991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23942 (or 23939 counting only the distinct ones).

The product of its digits is 40824, while the sum is 45.

The square root of 97811991 is about 9889.9944893817. The cubic root of 97811991 is about 460.7486093360.

The spelling of 97811991 in words is "ninety-seven million, eight hundred eleven thousand, nine hundred ninety-one".