16997921 has 2 divisors, whose sum is σ = 16997922. Its totient is φ = 16997920.

The previous prime is 16997917. The next prime is 16997947. The reversal of 16997921 is 12979961.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13140625 + 3857296 = 3625^2 + 1964^2 .

It is an emirp because it is prime and its reverse (12979961) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16997921 - 2² = 16997917 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16997521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8498960 + 8498961.

It is an arithmetic number, because the mean of its divisors is an integer number (8498961).

Almost surely, 2^16997921 is an apocalyptic number.

It is an amenable number.

16997921 is a deficient number, since it is larger than the sum of its proper divisors (1).

16997921 is an equidigital number, since it uses as much as digits as its factorization.

16997921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 61236, while the sum is 44.

The square root of 16997921 is about 4122.8535021269. The cubic root of 16997921 is about 257.1176768847.

The spelling of 16997921 in words is "sixteen million, nine hundred ninety-seven thousand, nine hundred twenty-one".