1221671809 has 16 divisors (see below), whose sum is σ = 1269930816. Its totient is φ = 1174305600.

The previous prime is 1221671791. The next prime is 1221671821. The reversal of 1221671809 is 9081761221.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221671809 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221671609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1487619 + ... + 1488439.

It is an arithmetic number, because the mean of its divisors is an integer number (79370676).

Almost surely, 2^1221671809 is an apocalyptic number.

It is an amenable number.

1221671809 is a deficient number, since it is larger than the sum of its proper divisors (48259007).

1221671809 is a wasteful number, since it uses less digits than its factorization.

1221671809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1296.

The product of its (nonzero) digits is 12096, while the sum is 37.

The square root of 1221671809 is about 34952.4220763025. The cubic root of 1221671809 is about 1069.0175886903.

The spelling of 1221671809 in words is "one billion, two hundred twenty-one million, six hundred seventy-one thousand, eight hundred nine".