18276721 has 2 divisors, whose sum is σ = 18276722. Its totient is φ = 18276720.

The previous prime is 18276707. The next prime is 18276761. The reversal of 18276721 is 12767281.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11971600 + 6305121 = 3460^2 + 2511^2 .

It is an emirp because it is prime and its reverse (12767281) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18276721 - 2⁷ = 18276593 is a prime.

It is not a weakly prime, because it can be changed into another prime (18276761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9138360 + 9138361.

It is an arithmetic number, because the mean of its divisors is an integer number (9138361).

Almost surely, 2^18276721 is an apocalyptic number.

It is an amenable number.

18276721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18276721 is an equidigital number, since it uses as much as digits as its factorization.

18276721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9408, while the sum is 34.

The square root of 18276721 is about 4275.1281852127. The cubic root of 18276721 is about 263.4103047261.

The spelling of 18276721 in words is "eighteen million, two hundred seventy-six thousand, seven hundred twenty-one".