81640369646 has 16 divisors (see below), whose sum is σ = 134331423408. Its totient is φ = 36904233600.

The previous prime is 81640369637. The next prime is 81640369651. The reversal of 81640369646 is 64696304618.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10247195 + ... + 10255158.

It is an arithmetic number, because the mean of its divisors is an integer number (8395713963).

Almost surely, 2^81640369646 is an apocalyptic number.

81640369646 is a deficient number, since it is larger than the sum of its proper divisors (52691053762).

81640369646 is a wasteful number, since it uses less digits than its factorization.

81640369646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20502547.

The product of its (nonzero) digits is 4478976, while the sum is 53.

The spelling of 81640369646 in words is "eighty-one billion, six hundred forty million, three hundred sixty-nine thousand, six hundred forty-six".