18149821 has 2 divisors, whose sum is σ = 18149822. Its totient is φ = 18149820.

The previous prime is 18149819. The next prime is 18149837. The reversal of 18149821 is 12894181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12924025 + 5225796 = 3595^2 + 2286^2 .

It is a cyclic number.

It is not a de Polignac number, because 18149821 - 2¹ = 18149819 is a prime.

Together with 18149819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18149851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9074910 + 9074911.

It is an arithmetic number, because the mean of its divisors is an integer number (9074911).

Almost surely, 2^18149821 is an apocalyptic number.

It is an amenable number.

18149821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18149821 is an equidigital number, since it uses as much as digits as its factorization.

18149821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 34.

The square root of 18149821 is about 4260.2606727758. The cubic root of 18149821 is about 262.7992463377.

The spelling of 18149821 in words is "eighteen million, one hundred forty-nine thousand, eight hundred twenty-one".