6640523381 has 2 divisors, whose sum is σ = 6640523382. Its totient is φ = 6640523380.

The previous prime is 6640523377. The next prime is 6640523387. The reversal of 6640523381 is 1833250466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6151892356 + 488631025 = 78434^2 + 22105^2 .

It is a cyclic number.

It is not a de Polignac number, because 6640523381 - 2² = 6640523377 is a prime.

It is a super-2 number, since 2×6640523381² = 88193101547215342322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6640523387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3320261690 + 3320261691.

It is an arithmetic number, because the mean of its divisors is an integer number (3320261691).

Almost surely, 2^6640523381 is an apocalyptic number.

It is an amenable number.

6640523381 is a deficient number, since it is larger than the sum of its proper divisors (1).

6640523381 is an equidigital number, since it uses as much as digits as its factorization.

6640523381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 103680, while the sum is 38.

The square root of 6640523381 is about 81489.4065569262. The cubic root of 6640523381 is about 1879.6086575090.

The spelling of 6640523381 in words is "six billion, six hundred forty million, five hundred twenty-three thousand, three hundred eighty-one".