1621318591 has 2 divisors, whose sum is σ = 1621318592. Its totient is φ = 1621318590.

The previous prime is 1621318579. The next prime is 1621318609. The reversal of 1621318591 is 1958131261.

It is a weak prime.

It is an emirp because it is prime and its reverse (1958131261) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1621318591 - 2⁹ = 1621318079 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1621318591.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1621318091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810659295 + 810659296.

It is an arithmetic number, because the mean of its divisors is an integer number (810659296).

Almost surely, 2^1621318591 is an apocalyptic number.

1621318591 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621318591 is an equidigital number, since it uses as much as digits as its factorization.

1621318591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 37.

The square root of 1621318591 is about 40265.6005915720. The cubic root of 1621318591 is about 1174.7788546539.

The spelling of 1621318591 in words is "one billion, six hundred twenty-one million, three hundred eighteen thousand, five hundred ninety-one".