17996821 has 2 divisors, whose sum is σ = 17996822. Its totient is φ = 17996820.

The previous prime is 17996813. The next prime is 17996831. The reversal of 17996821 is 12869971.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16719921 + 1276900 = 4089^2 + 1130^2 .

It is an emirp because it is prime and its reverse (12869971) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 17996821 - 2³ = 17996813 is a prime.

It is a super-2 number, since 2×17996821² = 647771132212082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (17996831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8998410 + 8998411.

It is an arithmetic number, because the mean of its divisors is an integer number (8998411).

Almost surely, 2^17996821 is an apocalyptic number.

It is an amenable number.

17996821 is a deficient number, since it is larger than the sum of its proper divisors (1).

17996821 is an equidigital number, since it uses as much as digits as its factorization.

17996821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54432, while the sum is 43.

The square root of 17996821 is about 4242.2660218331. The cubic root of 17996821 is about 262.0587101109.

The spelling of 17996821 in words is "seventeen million, nine hundred ninety-six thousand, eight hundred twenty-one".