9215991 has 8 divisors (see below), whose sum is σ = 13653360. Its totient is φ = 6143976.

The previous prime is 9215971. The next prime is 9216019. The reversal of 9215991 is 1995129.

It is a de Polignac number, because none of the positive numbers 2^k-9215991 is a prime.

It is a super-2 number, since 2×9215991² = 169868980224162, which contains 22 as substring.

9215991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (9215911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 170640 + ... + 170693.

It is an arithmetic number, because the mean of its divisors is an integer number (1706670).

Almost surely, 2^9215991 is an apocalyptic number.

9215991 is a deficient number, since it is larger than the sum of its proper divisors (4437369).

9215991 is a wasteful number, since it uses less digits than its factorization.

9215991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 341342 (or 341336 counting only the distinct ones).

The product of its digits is 7290, while the sum is 36.

The square root of 9215991 is about 3035.7850714436. The cubic root of 9215991 is about 209.6592432882.

It can be divided in two parts, 921599 and 1, that added together give a square (921600 = 960²).

The spelling of 9215991 in words is "nine million, two hundred fifteen thousand, nine hundred ninety-one".