18072421 has 2 divisors, whose sum is σ = 18072422. Its totient is φ = 18072420.

The previous prime is 18072403. The next prime is 18072437. The reversal of 18072421 is 12427081.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13616100 + 4456321 = 3690^2 + 2111^2 .

It is an emirp because it is prime and its reverse (12427081) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18072421 - 2⁵ = 18072389 is a prime.

It is a super-3 number, since 3×18072421³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18073421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9036210 + 9036211.

It is an arithmetic number, because the mean of its divisors is an integer number (9036211).

Almost surely, 2^18072421 is an apocalyptic number.

It is an amenable number.

18072421 is a deficient number, since it is larger than the sum of its proper divisors (1).

18072421 is an equidigital number, since it uses as much as digits as its factorization.

18072421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 18072421 is about 4251.1670162439. The cubic root of 18072421 is about 262.4251444912.

The spelling of 18072421 in words is "eighteen million, seventy-two thousand, four hundred twenty-one".