645623672081 has 2 divisors, whose sum is σ = 645623672082. Its totient is φ = 645623672080.

The previous prime is 645623672069. The next prime is 645623672093. The reversal of 645623672081 is 180276326546.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (645623672069) and next prime (645623672093).

It can be written as a sum of positive squares in only one way, i.e., 434406219025 + 211217453056 = 659095^2 + 459584^2 .

It is a cyclic number.

It is not a de Polignac number, because 645623672081 - 2¹⁴ = 645623655697 is a prime.

It is a super-2 number, since 2×645623672081² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (645623672011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322811836040 + 322811836041.

It is an arithmetic number, because the mean of its divisors is an integer number (322811836041).

Almost surely, 2^645623672081 is an apocalyptic number.

It is an amenable number.

645623672081 is a deficient number, since it is larger than the sum of its proper divisors (1).

645623672081 is an equidigital number, since it uses as much as digits as its factorization.

645623672081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2903040, while the sum is 50.

The spelling of 645623672081 in words is "six hundred forty-five billion, six hundred twenty-three million, six hundred seventy-two thousand, eighty-one".