644401261545157 has 2 divisors, whose sum is σ = 644401261545158. Its totient is φ = 644401261545156.

The previous prime is 644401261545133. The next prime is 644401261545161. The reversal of 644401261545157 is 751545162104446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 562923360712036 + 81477900833121 = 23726006^2 + 9026511^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644401261545157 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 644401261545098 and 644401261545107.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644401291545157) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322200630772578 + 322200630772579.

It is an arithmetic number, because the mean of its divisors is an integer number (322200630772579).

Almost surely, 2^{644401261545157} is an apocalyptic number.

It is an amenable number.

644401261545157 is a deficient number, since it is larger than the sum of its proper divisors (1).

644401261545157 is an equidigital number, since it uses as much as digits as its factorization.

644401261545157 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128000, while the sum is 55.

The spelling of 644401261545157 in words is "six hundred forty-four trillion, four hundred one billion, two hundred sixty-one million, five hundred forty-five thousand, one hundred fifty-seven".