991978076287 has 8 divisors (see below), whose sum is σ = 1082234050560. Its totient is φ = 901734793560.

The previous prime is 991978076233. The next prime is 991978076293. The reversal of 991978076287 is 782670879199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 991978076287 - 2²⁷ = 991843858559 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 (991978070287) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3009087 + ... + 3322432.

It is an arithmetic number, because the mean of its divisors is an integer number (135279256320).

Almost surely, 2^991978076287 is an apocalyptic number.

991978076287 is a deficient number, since it is larger than the sum of its proper divisors (90255974273).

991978076287 is a wasteful number, since it uses less digits than its factorization.

991978076287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6345773.

The product of its (nonzero) digits is 192036096, while the sum is 73.

The spelling of 991978076287 in words is "nine hundred ninety-one billion, nine hundred seventy-eight million, seventy-six thousand, two hundred eighty-seven".