16109561 has 4 divisors (see below), whose sum is σ = 17348772. Its totient is φ = 14870352.

The previous prime is 16109521. The next prime is 16109573. The reversal of 16109561 is 16590161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16590161 = 7 ⋅2370023.

It can be written as a sum of positive squares in 2 ways, for example, as 3400336 + 12709225 = 1844^2 + 3565^2 .

It is a cyclic number.

It is not a de Polignac number, because 16109561 - 2¹⁴ = 16093177 is a prime.

It is a super-2 number, since 2×16109561² = 519035911225442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16109501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 619586 + ... + 619611.

It is an arithmetic number, because the mean of its divisors is an integer number (4337193).

Almost surely, 2^16109561 is an apocalyptic number.

It is an amenable number.

16109561 is a deficient number, since it is larger than the sum of its proper divisors (1239211).

16109561 is a wasteful number, since it uses less digits than its factorization.

16109561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1239210.

The product of its (nonzero) digits is 1620, while the sum is 29.

The square root of 16109561 is about 4013.6717603710. The cubic root of 16109561 is about 252.5580613466.

It can be divided in two parts, 16 and 109561, that multiplied together give a square (1752976 = 1324²).

The spelling of 16109561 in words is "sixteen million, one hundred nine thousand, five hundred sixty-one".