1221679815 has 16 divisors (see below), whose sum is σ = 1961650656. Its totient is φ = 649241600.

The previous prime is 1221679787. The next prime is 1221679817. The reversal of 1221679815 is 5189761221.

It is not a de Polignac number, because 1221679815 - 2⁸ = 1221679559 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221679817) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 140706 + ... + 149135.

It is an arithmetic number, because the mean of its divisors is an integer number (122603166).

Almost surely, 2^1221679815 is an apocalyptic number.

1221679815 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1221679815 is a deficient number, since it is larger than the sum of its proper divisors (739970841).

1221679815 is a wasteful number, since it uses less digits than its factorization.

1221679815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290130.

The product of its digits is 60480, while the sum is 42.

The square root of 1221679815 is about 34952.5366032281. The cubic root of 1221679815 is about 1069.0199238881.

The spelling of 1221679815 in words is "one billion, two hundred twenty-one million, six hundred seventy-nine thousand, eight hundred fifteen".