17989721 has 2 divisors, whose sum is σ = 17989722. Its totient is φ = 17989720.

The previous prime is 17989709. The next prime is 17989747. The reversal of 17989721 is 12798971.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14167696 + 3822025 = 3764^2 + 1955^2 .

It is a cyclic number.

It is not a de Polignac number, because 17989721 - 2²² = 13795417 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (17989121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8994860 + 8994861.

It is an arithmetic number, because the mean of its divisors is an integer number (8994861).

Almost surely, 2^17989721 is an apocalyptic number.

It is an amenable number.

17989721 is a deficient number, since it is larger than the sum of its proper divisors (1).

17989721 is an equidigital number, since it uses as much as digits as its factorization.

17989721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 63504, while the sum is 44.

The square root of 17989721 is about 4241.4291223596. The cubic root of 17989721 is about 262.0242436242.

The spelling of 17989721 in words is "seventeen million, nine hundred eighty-nine thousand, seven hundred twenty-one".