1645226221 has 4 divisors (see below), whose sum is σ = 1742004252. Its totient is φ = 1548448192.

The previous prime is 1645226213. The next prime is 1645226239. The reversal of 1645226221 is 1226225461.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1226225461 = 3637 ⋅337153.

It can be written as a sum of positive squares in 2 ways, for example, as 929396196 + 715830025 = 30486^2 + 26755^2 .

It is a cyclic number.

It is not a de Polignac number, because 1645226221 - 2³ = 1645226213 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 (1645226251) 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, 48388990 + ... + 48389023.

It is an arithmetic number, because the mean of its divisors is an integer number (435501063).

Almost surely, 2^1645226221 is an apocalyptic number.

It is an amenable number.

1645226221 is a deficient number, since it is larger than the sum of its proper divisors (96778031).

1645226221 is an equidigital number, since it uses as much as digits as its factorization.

1645226221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96778030.

The product of its digits is 11520, while the sum is 31.

The square root of 1645226221 is about 40561.3883021772. The cubic root of 1645226221 is about 1180.5250514583.

The spelling of 1645226221 in words is "one billion, six hundred forty-five million, two hundred twenty-six thousand, two hundred twenty-one".