997921 has 4 divisors (see below), whose sum is σ = 1030144. Its totient is φ = 965700.

The previous prime is 997897. The next prime is 997933. The reversal of 997921 is 129799.

997921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 129799 = 293 ⋅443.

It is a cyclic number.

It is not a de Polignac number, because 997921 - 2⁵ = 997889 is a prime.

It is a Duffinian number.

997921 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (997961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16065 + ... + 16126.

It is an arithmetic number, because the mean of its divisors is an integer number (257536).

2⁹⁹⁷⁹²¹ is an apocalyptic number.

It is an amenable number.

997921 is a deficient number, since it is larger than the sum of its proper divisors (32223).

997921 is a wasteful number, since it uses less digits than its factorization.

997921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32222.

The product of its digits is 10206, while the sum is 37.

The square root of 997921 is about 998.9599591575. The cubic root of 997921 is about 99.9306519196.

Subtracting from 997921 its product of digits (10206), we obtain a triangular number (987715 = T₁₄₀₅).

It can be divided in two parts, 9979 and 21, that added together give a 4-th power (10000 = 10⁴).

The spelling of 997921 in words is "nine hundred ninety-seven thousand, nine hundred twenty-one".