65640793921 has 2 divisors, whose sum is σ = 65640793922. Its totient is φ = 65640793920.

The previous prime is 65640793877. The next prime is 65640793943. The reversal of 65640793921 is 12939704656.

It is a happy number.

65640793921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 33456433921 + 32184360000 = 182911^2 + 179400^2 .

It is a cyclic number.

It is not a de Polignac number, because 65640793921 - 2¹¹ = 65640791873 is a prime.

It is not a weakly prime, because it can be changed into another prime (65640793961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32820396960 + 32820396961.

It is an arithmetic number, because the mean of its divisors is an integer number (32820396961).

Almost surely, 2^65640793921 is an apocalyptic number.

It is an amenable number.

65640793921 is a deficient number, since it is larger than the sum of its proper divisors (1).

65640793921 is an equidigital number, since it uses as much as digits as its factorization.

65640793921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2449440, while the sum is 52.

The spelling of 65640793921 in words is "sixty-five billion, six hundred forty million, seven hundred ninety-three thousand, nine hundred twenty-one".