1221686845 has 4 divisors (see below), whose sum is σ = 1466024220. Its totient is φ = 977349472.

The previous prime is 1221686821. The next prime is 1221686887. The reversal of 1221686845 is 5486861221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5486861221 = 797 ⋅6884393.

It can be written as a sum of positive squares in 2 ways, for example, as 385493956 + 836192889 = 19634^2 + 28917^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221686845 - 2²³ = 1213298237 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 122168680 + ... + 122168689.

It is an arithmetic number, because the mean of its divisors is an integer number (366506055).

Almost surely, 2^1221686845 is an apocalyptic number.

It is an amenable number.

1221686845 is a deficient number, since it is larger than the sum of its proper divisors (244337375).

1221686845 is an equidigital number, since it uses as much as digits as its factorization.

1221686845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244337374.

The product of its digits is 184320, while the sum is 43.

The square root of 1221686845 is about 34952.6371680307. The cubic root of 1221686845 is about 1069.0219743969.

The spelling of 1221686845 in words is "one billion, two hundred twenty-one million, six hundred eighty-six thousand, eight hundred forty-five".