81511907 has 2 divisors, whose sum is σ = 81511908. Its totient is φ = 81511906.

The previous prime is 81511867. The next prime is 81511939. The reversal of 81511907 is 70911518.

It is an a-pointer prime, because the next prime (81511939) can be obtained adding 81511907 to its sum of digits (32).

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81511907 - 2¹⁰ = 81510883 is a prime.

It is not a weakly prime, because it can be changed into another prime (81511987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40755953 + 40755954.

It is an arithmetic number, because the mean of its divisors is an integer number (40755954).

Almost surely, 2^81511907 is an apocalyptic number.

81511907 is a deficient number, since it is larger than the sum of its proper divisors (1).

81511907 is an equidigital number, since it uses as much as digits as its factorization.

81511907 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 32.

The square root of 81511907 is about 9028.3944862860. The cubic root of 81511907 is about 433.5844362540.

The spelling of 81511907 in words is "eighty-one million, five hundred eleven thousand, nine hundred seven".