66824031581 has 4 divisors (see below), whose sum is σ = 66841378812. Its totient is φ = 66806684352.

The previous prime is 66824031563. The next prime is 66824031601. The reversal of 66824031581 is 18513042866.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 38386605625 + 28437425956 = 195925^2 + 168634^2 .

It is a cyclic number.

It is not a de Polignac number, because 66824031581 - 2¹⁸ = 66823769437 is a prime.

It is a super-2 number, since 2×66824031581² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66824001581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8667836 + ... + 8675541.

It is an arithmetic number, because the mean of its divisors is an integer number (16710344703).

Almost surely, 2^66824031581 is an apocalyptic number.

It is an amenable number.

66824031581 is a deficient number, since it is larger than the sum of its proper divisors (17347231).

66824031581 is a wasteful number, since it uses less digits than its factorization.

66824031581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17347230.

The product of its (nonzero) digits is 276480, while the sum is 44.

The spelling of 66824031581 in words is "sixty-six billion, eight hundred twenty-four million, thirty-one thousand, five hundred eighty-one".