645640051664 has 10 divisors (see below), whose sum is σ = 1250927600130. Its totient is φ = 322820025824.

The previous prime is 645640051663. The next prime is 645640051687. The reversal of 645640051664 is 466150046546.

It can be written as a sum of positive squares in only one way, i.e., 603200755600 + 42439296064 = 776660^2 + 206008^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645640051663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20176251599 + ... + 20176251630.

It is an arithmetic number, because the mean of its divisors is an integer number (125092760013).

Almost surely, 2^645640051664 is an apocalyptic number.

It is an amenable number.

645640051664 is a deficient number, since it is larger than the sum of its proper divisors (605287548466).

645640051664 is a wasteful number, since it uses less digits than its factorization.

645640051664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40352503237 (or 40352503231 counting only the distinct ones).

The product of its (nonzero) digits is 2073600, while the sum is 47.

The spelling of 645640051664 in words is "six hundred forty-five billion, six hundred forty million, fifty-one thousand, six hundred sixty-four".