18471821 has 2 divisors, whose sum is σ = 18471822. Its totient is φ = 18471820.

The previous prime is 18471793. The next prime is 18471863. The reversal of 18471821 is 12817481.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17757796 + 714025 = 4214^2 + 845^2 .

It is an emirp because it is prime and its reverse (12817481) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18471821 - 2⁶ = 18471757 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18471881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9235910 + 9235911.

It is an arithmetic number, because the mean of its divisors is an integer number (9235911).

Almost surely, 2^18471821 is an apocalyptic number.

It is an amenable number.

18471821 is a deficient number, since it is larger than the sum of its proper divisors (1).

18471821 is an equidigital number, since it uses as much as digits as its factorization.

18471821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3584, while the sum is 32.

The square root of 18471821 is about 4297.8856429645. The cubic root of 18471821 is about 264.3442717371.

The spelling of 18471821 in words is "eighteen million, four hundred seventy-one thousand, eight hundred twenty-one".