18927721 has 2 divisors, whose sum is σ = 18927722. Its totient is φ = 18927720.

The previous prime is 18927679. The next prime is 18927737. The reversal of 18927721 is 12772981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12110400 + 6817321 = 3480^2 + 2611^2 .

It is a cyclic number.

It is not a de Polignac number, because 18927721 - 2¹³ = 18919529 is a prime.

It is not a weakly prime, because it can be changed into another prime (18927791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9463860 + 9463861.

It is an arithmetic number, because the mean of its divisors is an integer number (9463861).

Almost surely, 2^18927721 is an apocalyptic number.

It is an amenable number.

18927721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18927721 is an equidigital number, since it uses as much as digits as its factorization.

18927721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14112, while the sum is 37.

The square root of 18927721 is about 4350.6000735531. The cubic root of 18927721 is about 266.5013675222.

The spelling of 18927721 in words is "eighteen million, nine hundred twenty-seven thousand, seven hundred twenty-one".