997991220 has 48 divisors (see below), whose sum is σ = 2796268608. Its totient is φ = 265950720.

The previous prime is 997991213. The next prime is 997991221. The reversal of 997991220 is 22199799.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 997991220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (997991221) 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, 100060 + ... + 109580.

It is an arithmetic number, because the mean of its divisors is an integer number (58255596).

Almost surely, 2^997991220 is an apocalyptic number.

It is an amenable number.

997991220 is an abundant number, since it is smaller than the sum of its proper divisors (1798277388).

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

997991220 is a wasteful number, since it uses less digits than its factorization.

997991220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11280 (or 11278 counting only the distinct ones).

The product of its (nonzero) digits is 183708, while the sum is 48.

The square root of 997991220 is about 31590.9990345351. Note that the first 3 decimals coincide. The cubic root of 997991220 is about 999.3299578104.

The spelling of 997991220 in words is "nine hundred ninety-seven million, nine hundred ninety-one thousand, two hundred twenty".