1279999721 has 16 divisors (see below), whose sum is σ = 1718602368. Its totient is φ = 920678400.

The previous prime is 1279999711. The next prime is 1279999727.

1279999721 is nontrivially palindromic in base 10.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1279999721 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1279999727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 638360 + ... + 640361.

It is an arithmetic number, because the mean of its divisors is an integer number (107412648).

Almost surely, 2^1279999721 is an apocalyptic number.

1279999721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1279999721 is a deficient number, since it is larger than the sum of its proper divisors (438602647).

1279999721 is a wasteful number, since it uses less digits than its factorization.

1279999721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1278752.

The product of its digits is 1285956, while the sum is 56.

The square root of 1279999721 is about 35777.0837408529. The cubic root of 1279999721 is about 1085.7669677502.

The spelling of 1279999721 in words is "one billion, two hundred seventy-nine million, nine hundred ninety-nine thousand, seven hundred twenty-one".