16661397 has 4 divisors (see below), whose sum is σ = 22215200. Its totient is φ = 11107596.

The previous prime is 16661369. The next prime is 16661401. The reversal of 16661397 is 79316661.

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: 79316661 = 3 ⋅26438887.

It is not a de Polignac number, because 16661397 - 2¹⁶ = 16595861 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 (16661317) 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, 2776897 + ... + 2776902.

It is an arithmetic number, because the mean of its divisors is an integer number (5553800).

Almost surely, 2^16661397 is an apocalyptic number.

It is an amenable number.

16661397 is a deficient number, since it is larger than the sum of its proper divisors (5553803).

16661397 is an equidigital number, since it uses as much as digits as its factorization.

16661397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5553802.

The product of its digits is 40824, while the sum is 39.

The square root of 16661397 is about 4081.8374538925. The cubic root of 16661397 is about 255.4095533249.

The spelling of 16661397 in words is "sixteen million, six hundred sixty-one thousand, three hundred ninety-seven".