997991280 has 480 divisors, whose sum is σ = 4094737920. Its totient is φ = 222704640.

The previous prime is 997991263. The next prime is 997991287. The reversal of 997991280 is 82199799.

It is a Cunningham number, because it is equal to 31591²-1.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (997991287) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2779741 + ... + 2780099.

It is an arithmetic number, because the mean of its divisors is an integer number (8530704).

Almost surely, 2^997991280 is an apocalyptic number.

997991280 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 997991280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2047368960).

997991280 is an abundant number, since it is smaller than the sum of its proper divisors (3096746640).

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

997991280 is a wasteful number, since it uses less digits than its factorization.

997991280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 411 (or 393 counting only the distinct ones).

The product of its (nonzero) digits is 734832, while the sum is 54.

The square root of 997991280 is about 31590.9999841727. Note that the first 4 decimals coincide. The cubic root of 997991280 is about 999.3299778372.

The spelling of 997991280 in words is "nine hundred ninety-seven million, nine hundred ninety-one thousand, two hundred eighty".