16991261 has 16 divisors (see below), whose sum is σ = 20189568. Its totient is φ = 13996800.

The previous prime is 16991237. The next prime is 16991281. The reversal of 16991261 is 16219961.

It is a cyclic number.

It is not a de Polignac number, because 16991261 - 2¹⁴ = 16974877 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16991201) 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, 20546 + ... + 21356.

It is an arithmetic number, because the mean of its divisors is an integer number (1261848).

Almost surely, 2^16991261 is an apocalyptic number.

It is an amenable number.

16991261 is a deficient number, since it is larger than the sum of its proper divisors (3198307).

16991261 is an equidigital number, since it uses as much as digits as its factorization.

16991261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 932.

The product of its digits is 5832, while the sum is 35.

The square root of 16991261 is about 4122.0457299744. The cubic root of 16991261 is about 257.0840918476.

The spelling of 16991261 in words is "sixteen million, nine hundred ninety-one thousand, two hundred sixty-one".