18234721 has 2 divisors, whose sum is σ = 18234722. Its totient is φ = 18234720.

The previous prime is 18234691. The next prime is 18234751. The reversal of 18234721 is 12743281.

It is a balanced prime because it is at equal distance from previous prime (18234691) and next prime (18234751).

It can be written as a sum of positive squares in only one way, i.e., 10595025 + 7639696 = 3255^2 + 2764^2 .

It is a cyclic number.

It is not a de Polignac number, because 18234721 - 2²³ = 9846113 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18234721.

It is not a weakly prime, because it can be changed into another prime (18234751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9117360 + 9117361.

It is an arithmetic number, because the mean of its divisors is an integer number (9117361).

Almost surely, 2^18234721 is an apocalyptic number.

It is an amenable number.

18234721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18234721 is an equidigital number, since it uses as much as digits as its factorization.

18234721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 28.

The square root of 18234721 is about 4270.2132265263. The cubic root of 18234721 is about 263.2083772197.

The spelling of 18234721 in words is "eighteen million, two hundred thirty-four thousand, seven hundred twenty-one".