16945981 has 4 divisors (see below), whose sum is σ = 18249532. Its totient is φ = 15642432.

The previous prime is 16945961. The next prime is 16946021. The reversal of 16945981 is 18954961.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18954961 = 73 ⋅259657.

It can be written as a sum of positive squares in 2 ways, for example, as 8213956 + 8732025 = 2866^2 + 2955^2 .

It is not a de Polignac number, because 16945981 - 2⁵ = 16945949 is a prime.

It is a super-2 number, since 2×16945981² = 574332544104722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16945931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 651756 + ... + 651781.

It is an arithmetic number, because the mean of its divisors is an integer number (4562383).

Almost surely, 2^16945981 is an apocalyptic number.

It is an amenable number.

16945981 is a deficient number, since it is larger than the sum of its proper divisors (1303551).

16945981 is a wasteful number, since it uses less digits than its factorization.

16945981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1303550.

The product of its digits is 77760, while the sum is 43.

The square root of 16945981 is about 4116.5496474596. The cubic root of 16945981 is about 256.8555209466.

The spelling of 16945981 in words is "sixteen million, nine hundred forty-five thousand, nine hundred eighty-one".