1657779806991 has 72 divisors (see below), whose sum is σ = 2960403064704. Its totient is φ = 815858537760.

The previous prime is 1657779806987. The next prime is 1657779807017. The reversal of 1657779806991 is 1996089777561.

It is not a de Polignac number, because 1657779806991 - 2² = 1657779806987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1657779804991) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 836235 + ... + 2003708.

It is an arithmetic number, because the mean of its divisors is an integer number (41116709232).

Almost surely, 2^{1657779806991} is an apocalyptic number.

1657779806991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1657779806991 is a deficient number, since it is larger than the sum of its proper divisors (1302623257713).

1657779806991 is a wasteful number, since it uses less digits than its factorization.

1657779806991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2840009 (or 2839983 counting only the distinct ones).

The product of its (nonzero) digits is 360067680, while the sum is 75.

The spelling of 1657779806991 in words is "one trillion, six hundred fifty-seven billion, seven hundred seventy-nine million, eight hundred six thousand, nine hundred ninety-one".