16520991 has 16 divisors (see below), whose sum is σ = 23895648. Its totient is φ = 10112000.

The previous prime is 16520951. The next prime is 16521023. The reversal of 16520991 is 19902561.

It is a cyclic number.

It is not a de Polignac number, because 16520991 - 2¹⁰ = 16519967 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16520921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1860 + ... + 6041.

It is an arithmetic number, because the mean of its divisors is an integer number (1493478).

Almost surely, 2^16520991 is an apocalyptic number.

16520991 is a deficient number, since it is larger than the sum of its proper divisors (7374657).

16520991 is a wasteful number, since it uses less digits than its factorization.

16520991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7962.

The product of its (nonzero) digits is 4860, while the sum is 33.

The square root of 16520991 is about 4064.6021945573. The cubic root of 16520991 is about 254.6900810031.

The spelling of 16520991 in words is "sixteen million, five hundred twenty thousand, nine hundred ninety-one".