1221691279 has 8 divisors (see below), whose sum is σ = 1287498240. Its totient is φ = 1156035096.

The previous prime is 1221691259. The next prime is 1221691283. The reversal of 1221691279 is 9721961221.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1221691279 - 2⁷ = 1221691151 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221691259) 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, 20857 + ... + 53650.

It is an arithmetic number, because the mean of its divisors is an integer number (160937280).

Almost surely, 2^1221691279 is an apocalyptic number.

1221691279 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

1221691279 is a deficient number, since it is larger than the sum of its proper divisors (65806961).

1221691279 is an equidigital number, since it uses as much as digits as its factorization.

1221691279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75389.

The product of its digits is 27216, while the sum is 40.

The square root of 1221691279 is about 34952.7005966635. The cubic root of 1221691279 is about 1069.0232677010.

The spelling of 1221691279 in words is "one billion, two hundred twenty-one million, six hundred ninety-one thousand, two hundred seventy-nine".