1213905809 has 8 divisors (see below), whose sum is σ = 1260441000. Its totient is φ = 1167682432.

The previous prime is 1213905767. The next prime is 1213905817. The reversal of 1213905809 is 9085093121.

It can be written as a sum of positive squares in 4 ways, for example, as 8427409 + 1205478400 = 2903^2 + 34720^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1213905809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1213305809) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 70004 + ... + 85605.

It is an arithmetic number, because the mean of its divisors is an integer number (157555125).

Almost surely, 2^1213905809 is an apocalyptic number.

It is an amenable number.

1213905809 is a deficient number, since it is larger than the sum of its proper divisors (46535191).

1213905809 is a wasteful number, since it uses less digits than its factorization.

1213905809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155907.

The product of its (nonzero) digits is 19440, while the sum is 38.

The square root of 1213905809 is about 34841.1510860362. The cubic root of 1213905809 is about 1066.7475724548.

The spelling of 1213905809 in words is "one billion, two hundred thirteen million, nine hundred five thousand, eight hundred nine".