16705721 has 2 divisors, whose sum is σ = 16705722. Its totient is φ = 16705720.

The previous prime is 16705709. The next prime is 16705729. The reversal of 16705721 is 12750761.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16687225 + 18496 = 4085^2 + 136^2 .

It is a cyclic number.

It is not a de Polignac number, because 16705721 - 2⁶ = 16705657 is a prime.

It is a super-2 number, since 2×16705721² = 558162228259682, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16705729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8352860 + 8352861.

It is an arithmetic number, because the mean of its divisors is an integer number (8352861).

Almost surely, 2^16705721 is an apocalyptic number.

It is an amenable number.

16705721 is a deficient number, since it is larger than the sum of its proper divisors (1).

16705721 is an equidigital number, since it uses as much as digits as its factorization.

16705721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2940, while the sum is 29.

The square root of 16705721 is about 4087.2632653158. The cubic root of 16705721 is about 255.6358398529.

The spelling of 16705721 in words is "sixteen million, seven hundred five thousand, seven hundred twenty-one".