1620431809 has 2 divisors, whose sum is σ = 1620431810. Its totient is φ = 1620431808.

The previous prime is 1620431803. The next prime is 1620431821. The reversal of 1620431809 is 9081340261.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1347257025 + 273174784 = 36705^2 + 16528^2 .

It is a cyclic number.

It is not a de Polignac number, because 1620431809 - 2¹³ = 1620423617 is a prime.

It is not a weakly prime, because it can be changed into another prime (1620431803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 810215904 + 810215905.

It is an arithmetic number, because the mean of its divisors is an integer number (810215905).

Almost surely, 2^1620431809 is an apocalyptic number.

It is an amenable number.

1620431809 is a deficient number, since it is larger than the sum of its proper divisors (1).

1620431809 is an equidigital number, since it uses as much as digits as its factorization.

1620431809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10368, while the sum is 34.

The square root of 1620431809 is about 40254.5874280187. The cubic root of 1620431809 is about 1174.5646333942.

The spelling of 1620431809 in words is "one billion, six hundred twenty million, four hundred thirty-one thousand, eight hundred nine".