81571507 has 2 divisors, whose sum is σ = 81571508. Its totient is φ = 81571506.

The previous prime is 81571489. The next prime is 81571517. The reversal of 81571507 is 70517518.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81571507 - 2¹⁵ = 81538739 is a prime.

It is not a weakly prime, because it can be changed into another prime (81571517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40785753 + 40785754.

It is an arithmetic number, because the mean of its divisors is an integer number (40785754).

Almost surely, 2^81571507 is an apocalyptic number.

81571507 is a deficient number, since it is larger than the sum of its proper divisors (1).

81571507 is an equidigital number, since it uses as much as digits as its factorization.

81571507 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9800, while the sum is 34.

The square root of 81571507 is about 9031.6945807528. The cubic root of 81571507 is about 433.6900868172.

The spelling of 81571507 in words is "eighty-one million, five hundred seventy-one thousand, five hundred seven".