188661721 has 2 divisors, whose sum is σ = 188661722. Its totient is φ = 188661720.

The previous prime is 188661703. The next prime is 188661757. The reversal of 188661721 is 127166881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 129140496 + 59521225 = 11364^2 + 7715^2 .

It is a cyclic number.

It is not a de Polignac number, because 188661721 - 2¹³ = 188653529 is a prime.

It is not a weakly prime, because it can be changed into another prime (188661761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 94330860 + 94330861.

It is an arithmetic number, because the mean of its divisors is an integer number (94330861).

Almost surely, 2^188661721 is an apocalyptic number.

It is an amenable number.

188661721 is a deficient number, since it is larger than the sum of its proper divisors (1).

188661721 is an equidigital number, since it uses as much as digits as its factorization.

188661721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 40.

The square root of 188661721 is about 13735.4184865260. The cubic root of 188661721 is about 573.5367670528.

The spelling of 188661721 in words is "one hundred eighty-eight million, six hundred sixty-one thousand, seven hundred twenty-one".