81771511 has 2 divisors, whose sum is σ = 81771512. Its totient is φ = 81771510.

The previous prime is 81771491. The next prime is 81771539. The reversal of 81771511 is 11517718.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81771511 - 2¹⁷ = 81640439 is a prime.

It is a super-2 number, since 2×81771511² = 13373160022446242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81771551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40885755 + 40885756.

It is an arithmetic number, because the mean of its divisors is an integer number (40885756).

Almost surely, 2^81771511 is an apocalyptic number.

81771511 is a deficient number, since it is larger than the sum of its proper divisors (1).

81771511 is an equidigital number, since it uses as much as digits as its factorization.

81771511 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1960, while the sum is 31.

The square root of 81771511 is about 9042.7601427883. The cubic root of 81771511 is about 434.0442503389.

The spelling of 81771511 in words is "eighty-one million, seven hundred seventy-one thousand, five hundred eleven".