1621521493 has 2 divisors, whose sum is σ = 1621521494. Its totient is φ = 1621521492.

The previous prime is 1621521463. The next prime is 1621521547. The reversal of 1621521493 is 3941251261.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1494440964 + 127080529 = 38658^2 + 11273^2 .

It is an emirp because it is prime and its reverse (3941251261) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1621521493 - 2⁹ = 1621520981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1621521463) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810760746 + 810760747.

It is an arithmetic number, because the mean of its divisors is an integer number (810760747).

Almost surely, 2^1621521493 is an apocalyptic number.

It is an amenable number.

1621521493 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621521493 is an equidigital number, since it uses as much as digits as its factorization.

1621521493 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 34.

The square root of 1621521493 is about 40268.1200579317. The cubic root of 1621521493 is about 1174.8278590132.

The spelling of 1621521493 in words is "one billion, six hundred twenty-one million, five hundred twenty-one thousand, four hundred ninety-three".