15801661 has 4 divisors (see below), whose sum is σ = 16311424. Its totient is φ = 15291900.

The previous prime is 15801649. The next prime is 15801677. The reversal of 15801661 is 16610851.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16610851 = 757 ⋅21943.

It is a cyclic number.

It is not a de Polignac number, because 15801661 - 2⁵ = 15801629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15801601) 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, 254835 + ... + 254896.

It is an arithmetic number, because the mean of its divisors is an integer number (4077856).

Almost surely, 2^15801661 is an apocalyptic number.

It is an amenable number.

15801661 is a deficient number, since it is larger than the sum of its proper divisors (509763).

15801661 is an equidigital number, since it uses as much as digits as its factorization.

15801661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 509762.

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 15801661 is about 3975.1303123294. The cubic root of 15801661 is about 250.9386632344.

The spelling of 15801661 in words is "fifteen million, eight hundred one thousand, six hundred sixty-one".