915989 has 4 divisors (see below), whose sum is σ = 918060. Its totient is φ = 913920.

The previous prime is 915973. The next prime is 915991. The reversal of 915989 is 989519.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 989519 = 17 ⋅58207.

It can be written as a sum of positive squares in 2 ways, for example, as 432964 + 483025 = 658^2 + 695^2 .

It is a cyclic number.

It is not a de Polignac number, because 915989 - 2⁴ = 915973 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (915919) 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, 74 + ... + 1355.

It is an arithmetic number, because the mean of its divisors is an integer number (229515).

2⁹¹⁵⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

915989 is a deficient number, since it is larger than the sum of its proper divisors (2071).

915989 is a wasteful number, since it uses less digits than its factorization.

915989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2070.

The product of its digits is 29160, while the sum is 41.

The square root of 915989 is about 957.0731424505. The cubic root of 915989 is about 97.1173341870.

The spelling of 915989 in words is "nine hundred fifteen thousand, nine hundred eighty-nine".