16561831 has 24 divisors (see below), whose sum is σ = 20027520. Its totient is φ = 13572000.

The previous prime is 16561823. The next prime is 16561847. The reversal of 16561831 is 13816561.

It is not a de Polignac number, because 16561831 - 2³ = 16561823 is a prime.

It is a super-2 number, since 2×16561831² = 548588492145122, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 16561793 and 16561802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561861) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 109606 + ... + 109756.

It is an arithmetic number, because the mean of its divisors is an integer number (834480).

Almost surely, 2^16561831 is an apocalyptic number.

16561831 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

16561831 is a deficient number, since it is larger than the sum of its proper divisors (3465689).

16561831 is a wasteful number, since it uses less digits than its factorization.

16561831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247 (or 234 counting only the distinct ones).

The product of its digits is 4320, while the sum is 31.

The square root of 16561831 is about 4069.6229555083. The cubic root of 16561831 is about 254.8997735041.

It can be divided in two parts, 165618 and 31, that added together give a square (165649 = 407²).

The spelling of 16561831 in words is "sixteen million, five hundred sixty-one thousand, eight hundred thirty-one".