1644503593981 has 2 divisors, whose sum is σ = 1644503593982. Its totient is φ = 1644503593980.

The previous prime is 1644503593907. The next prime is 1644503594009. The reversal of 1644503593981 is 1893953054461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1327816031481 + 316687562500 = 1152309^2 + 562750^2 .

It is a cyclic number.

It is not a de Polignac number, because 1644503593981 - 2¹⁵ = 1644503561213 is a prime.

It is a super-2 number, since 2×1644503593981² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1644503593181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 822251796990 + 822251796991.

It is an arithmetic number, because the mean of its divisors is an integer number (822251796991).

Almost surely, 2^{1644503593981} is an apocalyptic number.

It is an amenable number.

1644503593981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1644503593981 is an equidigital number, since it uses as much as digits as its factorization.

1644503593981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13996800, while the sum is 58.

The spelling of 1644503593981 in words is "one trillion, six hundred forty-four billion, five hundred three million, five hundred ninety-three thousand, nine hundred eighty-one".