188381821 has 2 divisors, whose sum is σ = 188381822. Its totient is φ = 188381820.

The previous prime is 188381819. The next prime is 188381849. The reversal of 188381821 is 128183881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 188073796 + 308025 = 13714^2 + 555^2 .

It is a cyclic number.

It is not a de Polignac number, because 188381821 - 2¹ = 188381819 is a prime.

Together with 188381819, 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 (188381881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 94190910 + 94190911.

It is an arithmetic number, because the mean of its divisors is an integer number (94190911).

Almost surely, 2^188381821 is an apocalyptic number.

It is an amenable number.

188381821 is a deficient number, since it is larger than the sum of its proper divisors (1).

188381821 is an equidigital number, since it uses as much as digits as its factorization.

188381821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24576, while the sum is 40.

The square root of 188381821 is about 13725.2257176339. The cubic root of 188381821 is about 573.2529921300.

The spelling of 188381821 in words is "one hundred eighty-eight million, three hundred eighty-one thousand, eight hundred twenty-one".