691242938891 has 4 divisors (see below), whose sum is σ = 691249860000. Its totient is φ = 691236017784.

The previous prime is 691242938887. The next prime is 691242938917. The reversal of 691242938891 is 198839242196.

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 691242938891 - 2² = 691242938887 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (691242938851) 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, 3308516 + ... + 3511233.

It is an arithmetic number, because the mean of its divisors is an integer number (172812465000).

Almost surely, 2^691242938891 is an apocalyptic number.

691242938891 is a deficient number, since it is larger than the sum of its proper divisors (6921109).

691242938891 is a wasteful number, since it uses less digits than its factorization.

691242938891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6921108.

The product of its digits is 13436928, while the sum is 62.

The spelling of 691242938891 in words is "six hundred ninety-one billion, two hundred forty-two million, nine hundred thirty-eight thousand, eight hundred ninety-one".