81919247 has 2 divisors, whose sum is σ = 81919248. Its totient is φ = 81919246.

The previous prime is 81919231. The next prime is 81919259. The reversal of 81919247 is 74291918.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81919247 - 2⁴ = 81919231 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81919297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40959623 + 40959624.

It is an arithmetic number, because the mean of its divisors is an integer number (40959624).

Almost surely, 2^81919247 is an apocalyptic number.

81919247 is a deficient number, since it is larger than the sum of its proper divisors (1).

81919247 is an equidigital number, since it uses as much as digits as its factorization.

81919247 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 41.

The square root of 81919247 is about 9050.9252013261. The cubic root of 81919247 is about 434.3054879503.

The spelling of 81919247 in words is "eighty-one million, nine hundred nineteen thousand, two hundred forty-seven".