87721391 has 2 divisors, whose sum is σ = 87721392. Its totient is φ = 87721390.

The previous prime is 87721367. The next prime is 87721397. The reversal of 87721391 is 19312778.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-87721391 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 (87721397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43860695 + 43860696.

It is an arithmetic number, because the mean of its divisors is an integer number (43860696).

Almost surely, 2^87721391 is an apocalyptic number.

87721391 is a deficient number, since it is larger than the sum of its proper divisors (1).

87721391 is an equidigital number, since it uses as much as digits as its factorization.

87721391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21168, while the sum is 38.

The square root of 87721391 is about 9365.9698376623. The cubic root of 87721391 is about 444.3261121059.

The spelling of 87721391 in words is "eighty-seven million, seven hundred twenty-one thousand, three hundred ninety-one".