81645667 has 2 divisors, whose sum is σ = 81645668. Its totient is φ = 81645666.

The previous prime is 81645649. The next prime is 81645671. The reversal of 81645667 is 76654618.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81645667 - 2¹⁵ = 81612899 is a prime.

It is equal to p_4759972 and since 81645667 and 4759972 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81645647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40822833 + 40822834.

It is an arithmetic number, because the mean of its divisors is an integer number (40822834).

Almost surely, 2^81645667 is an apocalyptic number.

81645667 is a deficient number, since it is larger than the sum of its proper divisors (1).

81645667 is an equidigital number, since it uses as much as digits as its factorization.

81645667 is an evil number, because the sum of its binary digits is even.

The product of its digits is 241920, while the sum is 43.

The square root of 81645667 is about 9035.7991898891. The cubic root of 81645667 is about 433.8214754855.

It can be divided in two parts, 8164 and 5667, that added together give a palindrome (13831).

The spelling of 81645667 in words is "eighty-one million, six hundred forty-five thousand, six hundred sixty-seven".