64947721789 has 4 divisors (see below), whose sum is σ = 66173150556. Its totient is φ = 63722293024.

The previous prime is 64947721781. The next prime is 64947721801. The reversal of 64947721789 is 98712774946.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 98712774946 = 2 ⋅49356387473.

It can be written as a sum of positive squares in 2 ways, for example, as 32881656889 + 32066064900 = 181333^2 + 179070^2 .

It is a cyclic number.

It is not a de Polignac number, because 64947721789 - 2³ = 64947721781 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 64947721789.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64947721781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 612714304 + ... + 612714409.

It is an arithmetic number, because the mean of its divisors is an integer number (16543287639).

Almost surely, 2^64947721789 is an apocalyptic number.

It is an amenable number.

64947721789 is a deficient number, since it is larger than the sum of its proper divisors (1225428767).

64947721789 is a wasteful number, since it uses less digits than its factorization.

64947721789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1225428766.

The product of its digits is 42674688, while the sum is 64.

The spelling of 64947721789 in words is "sixty-four billion, nine hundred forty-seven million, seven hundred twenty-one thousand, seven hundred eighty-nine".