18693721 has 2 divisors, whose sum is σ = 18693722. Its totient is φ = 18693720.

The previous prime is 18693709. The next prime is 18693749. The reversal of 18693721 is 12739681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18147600 + 546121 = 4260^2 + 739^2 .

It is a cyclic number.

It is not a de Polignac number, because 18693721 - 2⁹ = 18693209 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18693791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9346860 + 9346861.

It is an arithmetic number, because the mean of its divisors is an integer number (9346861).

Almost surely, 2^18693721 is an apocalyptic number.

It is an amenable number.

18693721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18693721 is an equidigital number, since it uses as much as digits as its factorization.

18693721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 37.

The square root of 18693721 is about 4323.6235960130. The cubic root of 18693721 is about 265.3985743055.

The spelling of 18693721 in words is "eighteen million, six hundred ninety-three thousand, seven hundred twenty-one".