17991121 has 4 divisors (see below), whose sum is σ = 18050032. Its totient is φ = 17932212.

The previous prime is 17991109. The next prime is 17991131. The reversal of 17991121 is 12119971.

It is a happy number.

17991121 is nontrivially palindromic in base 15.

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: 12119971 = 73 ⋅166027.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-17991121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (17991131) 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, 28995 + ... + 29608.

It is an arithmetic number, because the mean of its divisors is an integer number (4512508).

Almost surely, 2^17991121 is an apocalyptic number.

It is an amenable number.

17991121 is a deficient number, since it is larger than the sum of its proper divisors (58911).

17991121 is an equidigital number, since it uses as much as digits as its factorization.

17991121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58910.

The product of its digits is 1134, while the sum is 31.

The square root of 17991121 is about 4241.5941578609. The cubic root of 17991121 is about 262.0310405505.

The spelling of 17991121 in words is "seventeen million, nine hundred ninety-one thousand, one hundred twenty-one".