1621009813 has 2 divisors, whose sum is σ = 1621009814. Its totient is φ = 1621009812.

The previous prime is 1621009759. The next prime is 1621009843. The reversal of 1621009813 is 3189001261.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1295496049 + 325513764 = 35993^2 + 18042^2 .

It is an emirp because it is prime and its reverse (3189001261) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1621009813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1621009843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810504906 + 810504907.

It is an arithmetic number, because the mean of its divisors is an integer number (810504907).

Almost surely, 2^1621009813 is an apocalyptic number.

It is an amenable number.

1621009813 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621009813 is an equidigital number, since it uses as much as digits as its factorization.

1621009813 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 1621009813 is about 40261.7661435760. The cubic root of 1621009813 is about 1174.7042715548.

The spelling of 1621009813 in words is "one billion, six hundred twenty-one million, nine thousand, eight hundred thirteen".