86721781 has 2 divisors, whose sum is σ = 86721782. Its totient is φ = 86721780.

The previous prime is 86721763. The next prime is 86721793. The reversal of 86721781 is 18712768.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70392100 + 16329681 = 8390^2 + 4041^2 .

It is a cyclic number.

It is not a de Polignac number, because 86721781 - 2⁵ = 86721749 is a prime.

It is a super-2 number, since 2×86721781² = 15041334599623922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (86721751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43360890 + 43360891.

It is an arithmetic number, because the mean of its divisors is an integer number (43360891).

Almost surely, 2^86721781 is an apocalyptic number.

It is an amenable number.

86721781 is a deficient number, since it is larger than the sum of its proper divisors (1).

86721781 is an equidigital number, since it uses as much as digits as its factorization.

86721781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37632, while the sum is 40.

The square root of 86721781 is about 9312.4530065928. The cubic root of 86721781 is about 442.6319199811.

The spelling of 86721781 in words is "eighty-six million, seven hundred twenty-one thousand, seven hundred eighty-one".