991566628542 has 32 divisors (see below), whose sum is σ = 2518264454400. Its totient is φ = 283304750904.

The previous prime is 991566628531. The next prime is 991566628543. The reversal of 991566628542 is 245826665199.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a self number, because there is not a number n which added to its sum of digits gives 991566628542.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991566628543) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1311595692 + ... + 1311596447.

It is an arithmetic number, because the mean of its divisors is an integer number (78695764200).

Almost surely, 2^991566628542 is an apocalyptic number.

991566628542 is an abundant number, since it is smaller than the sum of its proper divisors (1526697825858).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991566628542 is a wasteful number, since it uses less digits than its factorization.

991566628542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2623192157 (or 2623192151 counting only the distinct ones).

The product of its digits is 55987200, while the sum is 63.

The spelling of 991566628542 in words is "nine hundred ninety-one billion, five hundred sixty-six million, six hundred twenty-eight thousand, five hundred forty-two".