16657121 has 4 divisors (see below), whose sum is σ = 17938452. Its totient is φ = 15375792.

The previous prime is 16657117. The next prime is 16657153. The reversal of 16657121 is 12175661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12175661 = 61 ⋅199601.

It can be written as a sum of positive squares in 2 ways, for example, as 8042896 + 8614225 = 2836^2 + 2935^2 .

It is a cyclic number.

It is not a de Polignac number, because 16657121 - 2² = 16657117 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16657181) 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, 640646 + ... + 640671.

It is an arithmetic number, because the mean of its divisors is an integer number (4484613).

Almost surely, 2^16657121 is an apocalyptic number.

It is an amenable number.

16657121 is a deficient number, since it is larger than the sum of its proper divisors (1281331).

16657121 is a wasteful number, since it uses less digits than its factorization.

16657121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1281330.

The product of its digits is 2520, while the sum is 29.

The square root of 16657121 is about 4081.3136365636. The cubic root of 16657121 is about 255.3877019221.

The spelling of 16657121 in words is "sixteen million, six hundred fifty-seven thousand, one hundred twenty-one".