1645503055621 has 2 divisors, whose sum is σ = 1645503055622. Its totient is φ = 1645503055620.

The previous prime is 1645503055607. The next prime is 1645503055663. The reversal of 1645503055621 is 1265503055461.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1643744511396 + 1758544225 = 1282086^2 + 41935^2 .

It is an emirp because it is prime and its reverse (1265503055461) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1645503055621 - 2³⁹ = 1095747241733 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1645503055421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 822751527810 + 822751527811.

It is an arithmetic number, because the mean of its divisors is an integer number (822751527811).

Almost surely, 2^{1645503055621} is an apocalyptic number.

It is an amenable number.

1645503055621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1645503055621 is an equidigital number, since it uses as much as digits as its factorization.

1645503055621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 540000, while the sum is 43.

The spelling of 1645503055621 in words is "one trillion, six hundred forty-five billion, five hundred three million, fifty-five thousand, six hundred twenty-one".