1221856747 has 4 divisors (see below), whose sum is σ = 1225378296. Its totient is φ = 1218335200.

The previous prime is 1221856721. The next prime is 1221856799. The reversal of 1221856747 is 7476581221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7476581221 = 62473 ⋅119677.

It is a cyclic number.

It is not a de Polignac number, because 1221856747 - 2⁷ = 1221856619 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221854747) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1760254 + ... + 1760947.

It is an arithmetic number, because the mean of its divisors is an integer number (306344574).

Almost surely, 2^1221856747 is an apocalyptic number.

1221856747 is a deficient number, since it is larger than the sum of its proper divisors (3521549).

1221856747 is an equidigital number, since it uses as much as digits as its factorization.

1221856747 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3521548.

The product of its digits is 188160, while the sum is 43.

The square root of 1221856747 is about 34955.0675439199. The cubic root of 1221856747 is about 1069.0715289815.

The spelling of 1221856747 in words is "one billion, two hundred twenty-one million, eight hundred fifty-six thousand, seven hundred forty-seven".