17990721 has 16 divisors (see below), whose sum is σ = 30460800. Its totient is φ = 10280304.

The previous prime is 17990689. The next prime is 17990723. The reversal of 17990721 is 12709971.

It is not a de Polignac number, because 17990721 - 2⁵ = 17990689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (17990723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47406 + ... + 47783.

It is an arithmetic number, because the mean of its divisors is an integer number (1903800).

Almost surely, 2^17990721 is an apocalyptic number.

It is an amenable number.

17990721 is a deficient number, since it is larger than the sum of its proper divisors (12470079).

17990721 is an equidigital number, since it uses as much as digits as its factorization.

17990721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95205 (or 95199 counting only the distinct ones).

The product of its (nonzero) digits is 7938, while the sum is 36.

The square root of 17990721 is about 4241.5470055158. The cubic root of 17990721 is about 262.0290986075.

The spelling of 17990721 in words is "seventeen million, nine hundred ninety thousand, seven hundred twenty-one".