81691741 has 2 divisors, whose sum is σ = 81691742. Its totient is φ = 81691740.

The previous prime is 81691739. The next prime is 81691747. The reversal of 81691741 is 14719618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81631225 + 60516 = 9035^2 + 246^2 .

It is a cyclic number.

It is not a de Polignac number, because 81691741 - 2¹ = 81691739 is a prime.

It is a super-2 number, since 2×81691741² = 13347081095222162, which contains 22 as substring.

Together with 81691739, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 81691741.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81691747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40845870 + 40845871.

It is an arithmetic number, because the mean of its divisors is an integer number (40845871).

Almost surely, 2^81691741 is an apocalyptic number.

It is an amenable number.

81691741 is a deficient number, since it is larger than the sum of its proper divisors (1).

81691741 is an equidigital number, since it uses as much as digits as its factorization.

81691741 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 37.

The square root of 81691741 is about 9038.3483557562. The cubic root of 81691741 is about 433.9030643509.

The spelling of 81691741 in words is "eighty-one million, six hundred ninety-one thousand, seven hundred forty-one".