187717921 has 2 divisors, whose sum is σ = 187717922. Its totient is φ = 187717920.

The previous prime is 187717903. The next prime is 187717969. The reversal of 187717921 is 129717781.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 128504896 + 59213025 = 11336^2 + 7695^2 .

It is a cyclic number.

It is not a de Polignac number, because 187717921 - 2²³ = 179329313 is a prime.

It is not a weakly prime, because it can be changed into another prime (187717991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 93858960 + 93858961.

It is an arithmetic number, because the mean of its divisors is an integer number (93858961).

Almost surely, 2^187717921 is an apocalyptic number.

It is an amenable number.

187717921 is a deficient number, since it is larger than the sum of its proper divisors (1).

187717921 is an equidigital number, since it uses as much as digits as its factorization.

187717921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 49392, while the sum is 43.

The square root of 187717921 is about 13701.0189767039. The cubic root of 187717921 is about 572.5787752245.

The spelling of 187717921 in words is "one hundred eighty-seven million, seven hundred seventeen thousand, nine hundred twenty-one".