18049721 has 2 divisors, whose sum is σ = 18049722. Its totient is φ = 18049720.

The previous prime is 18049709. The next prime is 18049727. The reversal of 18049721 is 12794081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12924025 + 5125696 = 3595^2 + 2264^2 .

It is a cyclic number.

It is not a de Polignac number, because 18049721 - 2¹⁸ = 17787577 is a prime.

It is not a weakly prime, because it can be changed into another prime (18049727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9024860 + 9024861.

It is an arithmetic number, because the mean of its divisors is an integer number (9024861).

Almost surely, 2^18049721 is an apocalyptic number.

It is an amenable number.

18049721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18049721 is an equidigital number, since it uses as much as digits as its factorization.

18049721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 18049721 is about 4248.4963222298. The cubic root of 18049721 is about 262.3152247659.

The spelling of 18049721 in words is "eighteen million, forty-nine thousand, seven hundred twenty-one".