187381721 has 2 divisors, whose sum is σ = 187381722. Its totient is φ = 187381720.

The previous prime is 187381697. The next prime is 187381723. The reversal of 187381721 is 127183781.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 133726096 + 53655625 = 11564^2 + 7325^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-187381721 is a prime.

It is a super-2 number, since 2×187381721² = 70223818729843682, which contains 22 as substring.

Together with 187381723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (187381723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 93690860 + 93690861.

It is an arithmetic number, because the mean of its divisors is an integer number (93690861).

Almost surely, 2^187381721 is an apocalyptic number.

It is an amenable number.

187381721 is a deficient number, since it is larger than the sum of its proper divisors (1).

187381721 is an equidigital number, since it uses as much as digits as its factorization.

187381721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18816, while the sum is 38.

The square root of 187381721 is about 13688.7443178693. The cubic root of 187381721 is about 572.2367442669.

The spelling of 187381721 in words is "one hundred eighty-seven million, three hundred eighty-one thousand, seven hundred twenty-one".