81511669 has 2 divisors, whose sum is σ = 81511670. Its totient is φ = 81511668.

The previous prime is 81511631. The next prime is 81511673. The reversal of 81511669 is 96611518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72897444 + 8614225 = 8538^2 + 2935^2 .

It is a cyclic number.

It is not a de Polignac number, because 81511669 - 2⁷ = 81511541 is a prime.

It is a super-2 number, since 2×81511669² = 13288304366331122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81511069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40755834 + 40755835.

It is an arithmetic number, because the mean of its divisors is an integer number (40755835).

Almost surely, 2^81511669 is an apocalyptic number.

It is an amenable number.

81511669 is a deficient number, since it is larger than the sum of its proper divisors (1).

81511669 is an equidigital number, since it uses as much as digits as its factorization.

81511669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 37.

The square root of 81511669 is about 9028.3813056383. The cubic root of 81511669 is about 433.5840142576.

The spelling of 81511669 in words is "eighty-one million, five hundred eleven thousand, six hundred sixty-nine".