18435721 has 2 divisors, whose sum is σ = 18435722. Its totient is φ = 18435720.

The previous prime is 18435713. The next prime is 18435733. The reversal of 18435721 is 12753481.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15840400 + 2595321 = 3980^2 + 1611^2 .

It is a cyclic number.

It is not a de Polignac number, because 18435721 - 2³ = 18435713 is a prime.

It is not a weakly prime, because it can be changed into another prime (18435751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9217860 + 9217861.

It is an arithmetic number, because the mean of its divisors is an integer number (9217861).

Almost surely, 2^18435721 is an apocalyptic number.

It is an amenable number.

18435721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18435721 is an equidigital number, since it uses as much as digits as its factorization.

18435721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6720, while the sum is 31.

The square root of 18435721 is about 4293.6838495632. The cubic root of 18435721 is about 264.1719542817.

The spelling of 18435721 in words is "eighteen million, four hundred thirty-five thousand, seven hundred twenty-one".