997771891 has 4 divisors (see below), whose sum is σ = 998389800. Its totient is φ = 997153984.

The previous prime is 997771889. The next prime is 997771903. The reversal of 997771891 is 198177799.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 997771891 - 2¹ = 997771889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (997771861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 306526 + ... + 309763.

It is an arithmetic number, because the mean of its divisors is an integer number (249597450).

Almost surely, 2^997771891 is an apocalyptic number.

997771891 is a deficient number, since it is larger than the sum of its proper divisors (617909).

997771891 is a wasteful number, since it uses less digits than its factorization.

997771891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 617908.

The product of its digits is 2000376, while the sum is 58.

The square root of 997771891 is about 31587.5274594261. The cubic root of 997771891 is about 999.2567447084.

The spelling of 997771891 in words is "nine hundred ninety-seven million, seven hundred seventy-one thousand, eight hundred ninety-one".