68891991 has 12 divisors (see below), whose sum is σ = 106853112. Its totient is φ = 39366768.

The previous prime is 68891987. The next prime is 68892037. The reversal of 68891991 is 19919886.

It is a happy number.

It is not a de Polignac number, because 68891991 - 2² = 68891987 is a prime.

It is a super-2 number, since 2×68891991² = 9492212847888162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (68891971) 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, 234180 + ... + 234473.

It is an arithmetic number, because the mean of its divisors is an integer number (8904426).

Almost surely, 2^68891991 is an apocalyptic number.

68891991 is a deficient number, since it is larger than the sum of its proper divisors (37961121).

68891991 is a wasteful number, since it uses less digits than its factorization.

68891991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 468670 (or 468663 counting only the distinct ones).

The product of its digits is 279936, while the sum is 51.

The square root of 68891991 is about 8300.1199388924. The cubic root of 68891991 is about 409.9424686279.

The spelling of 68891991 in words is "sixty-eight million, eight hundred ninety-one thousand, nine hundred ninety-one".