997561 has 4 divisors (see below), whose sum is σ = 1006992. Its totient is φ = 988132.

The previous prime is 997553. The next prime is 997573. The reversal of 997561 is 165799.

997561 = T₈₁₄ + T₈₁₅ + T₈₁₆.

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.

It is a cyclic number.

It is not a de Polignac number, because 997561 - 2³ = 997553 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 997561.

It is not an unprimeable number, because it can be changed into a prime (997511) 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, 4555 + ... + 4768.

It is an arithmetic number, because the mean of its divisors is an integer number (251748).

2⁹⁹⁷⁵⁶¹ is an apocalyptic number.

997561 is the 816-th centered triangular number.

It is an amenable number.

997561 is a deficient number, since it is larger than the sum of its proper divisors (9431).

997561 is a wasteful number, since it uses less digits than its factorization.

997561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9430.

The product of its digits is 17010, while the sum is 37.

The square root of 997561 is about 998.7797555017. The cubic root of 997561 is about 99.9186338134.

The spelling of 997561 in words is "nine hundred ninety-seven thousand, five hundred sixty-one".