997920 has 240 divisors, whose sum is σ = 4390848. Its totient is φ = 207360.

The previous prime is 997897. The next prime is 997933. The reversal of 997920 is 29799.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nialpdrome in base 6.

It is a zygodrome in base 6.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 997920.

It is an unprimeable number.

997920 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 90715 + ... + 90725.

2⁹⁹⁷⁹²⁰ is an apocalyptic number.

997920 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 997920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2195424).

997920 is an abundant number, since it is smaller than the sum of its proper divisors (3392928).

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

997920 is a wasteful number, since it uses less digits than its factorization.

997920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45 (or 28 counting only the distinct ones).

The product of its (nonzero) digits is 10206, while the sum is 36.

The square root of 997920 is about 998.9594586368. The cubic root of 997920 is about 99.9306185399.

It can be divided in two parts, 9979 and 20, that added together give a palindrome (9999).

The spelling of 997920 in words is "nine hundred ninety-seven thousand, nine hundred twenty".