16721657 has 2 divisors, whose sum is σ = 16721658. Its totient is φ = 16721656.

The previous prime is 16721651. The next prime is 16721671. The reversal of 16721657 is 75612761.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8404201 + 8317456 = 2899^2 + 2884^2 .

It is a cyclic number.

It is not a de Polignac number, because 16721657 - 2⁴ = 16721641 is a prime.

It is a super-2 number, since 2×16721657² = 559227625651298, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (16721651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8360828 + 8360829.

It is an arithmetic number, because the mean of its divisors is an integer number (8360829).

Almost surely, 2^16721657 is an apocalyptic number.

It is an amenable number.

16721657 is a deficient number, since it is larger than the sum of its proper divisors (1).

16721657 is an equidigital number, since it uses as much as digits as its factorization.

16721657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17640, while the sum is 35.

The square root of 16721657 is about 4089.2122713305. The cubic root of 16721657 is about 255.7170998009.

The spelling of 16721657 in words is "sixteen million, seven hundred twenty-one thousand, six hundred fifty-seven".