991002197772 has 18 divisors (see below), whose sum is σ = 2505033333348. Its totient is φ = 330334065912.

The previous prime is 991002197767. The next prime is 991002197807. The reversal of 991002197772 is 277791200199.

It is a tau number, because it is divible by the number of its divisors (18).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13763919378 + ... + 13763919449.

Almost surely, 2^991002197772 is an apocalyptic number.

It is an amenable number.

991002197772 is an abundant number, since it is smaller than the sum of its proper divisors (1514031135576).

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

991002197772 is a wasteful number, since it uses less digits than its factorization.

991002197772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27527838837 (or 27527838832 counting only the distinct ones).

The product of its (nonzero) digits is 1000188, while the sum is 54.

The spelling of 991002197772 in words is "nine hundred ninety-one billion, two million, one hundred ninety-seven thousand, seven hundred seventy-two".