81748991 has 2 divisors, whose sum is σ = 81748992. Its totient is φ = 81748990.

The previous prime is 81748987. The next prime is 81748993. The reversal of 81748991 is 19984718.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81748991 - 2² = 81748987 is a prime.

Together with 81748993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81748993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40874495 + 40874496.

It is an arithmetic number, because the mean of its divisors is an integer number (40874496).

Almost surely, 2^81748991 is an apocalyptic number.

81748991 is a deficient number, since it is larger than the sum of its proper divisors (1).

81748991 is an equidigital number, since it uses as much as digits as its factorization.

81748991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 47.

The square root of 81748991 is about 9041.5148620129. The cubic root of 81748991 is about 434.0044011956.

The spelling of 81748991 in words is "eighty-one million, seven hundred forty-eight thousand, nine hundred ninety-one".