1621091565109 has 2 divisors, whose sum is σ = 1621091565110. Its totient is φ = 1621091565108.

The previous prime is 1621091565061. The next prime is 1621091565133. The reversal of 1621091565109 is 9015651901261.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1017949834225 + 603141730884 = 1008935^2 + 776622^2 .

It is an emirp because it is prime and its reverse (9015651901261) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1621091565109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1621091565199) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810545782554 + 810545782555.

It is an arithmetic number, because the mean of its divisors is an integer number (810545782555).

Almost surely, 2^{1621091565109} is an apocalyptic number.

It is an amenable number.

1621091565109 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621091565109 is an equidigital number, since it uses as much as digits as its factorization.

1621091565109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 145800, while the sum is 46.

The spelling of 1621091565109 in words is "one trillion, six hundred twenty-one billion, ninety-one million, five hundred sixty-five thousand, one hundred nine".