1641520355921 has 2 divisors, whose sum is σ = 1641520355922. Its totient is φ = 1641520355920.

The previous prime is 1641520355831. The next prime is 1641520355947. The reversal of 1641520355921 is 1295530251461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 879635776321 + 761884579600 = 937889^2 + 872860^2 .

It is an emirp because it is prime and its reverse (1295530251461) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1641520355921 - 2¹⁸ = 1641520093777 is a prime.

It is not a weakly prime, because it can be changed into another prime (1641520355621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 820760177960 + 820760177961.

It is an arithmetic number, because the mean of its divisors is an integer number (820760177961).

Almost surely, 2^{1641520355921} is an apocalyptic number.

It is an amenable number.

1641520355921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1641520355921 is an equidigital number, since it uses as much as digits as its factorization.

1641520355921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324000, while the sum is 44.

The spelling of 1641520355921 in words is "one trillion, six hundred forty-one billion, five hundred twenty million, three hundred fifty-five thousand, nine hundred twenty-one".