81447913 has 2 divisors, whose sum is σ = 81447914. Its totient is φ = 81447912.

The previous prime is 81447887. The next prime is 81447917. The reversal of 81447913 is 31974418.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64448784 + 16999129 = 8028^2 + 4123^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81447913 is a prime.

It is not a weakly prime, because it can be changed into another prime (81447917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40723956 + 40723957.

It is an arithmetic number, because the mean of its divisors is an integer number (40723957).

Almost surely, 2^81447913 is an apocalyptic number.

It is an amenable number.

81447913 is a deficient number, since it is larger than the sum of its proper divisors (1).

81447913 is an equidigital number, since it uses as much as digits as its factorization.

81447913 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 37.

The square root of 81447913 is about 9024.8497494418. The cubic root of 81447913 is about 433.4709392700.

The spelling of 81447913 in words is "eighty-one million, four hundred forty-seven thousand, nine hundred thirteen".