1643264521 has 4 divisors (see below), whose sum is σ = 1653731332. Its totient is φ = 1632797712.

The previous prime is 1643264501. The next prime is 1643264527. The reversal of 1643264521 is 1254623461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 394419600 + 1248844921 = 19860^2 + 35339^2 .

It is a cyclic number.

It is not a de Polignac number, because 1643264521 - 2¹¹ = 1643262473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1643264527) 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, 5233170 + ... + 5233483.

It is an arithmetic number, because the mean of its divisors is an integer number (413432833).

Almost surely, 2^1643264521 is an apocalyptic number.

It is an amenable number.

1643264521 is a deficient number, since it is larger than the sum of its proper divisors (10466811).

1643264521 is a wasteful number, since it uses less digits than its factorization.

1643264521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10466810.

The product of its digits is 34560, while the sum is 34.

The square root of 1643264521 is about 40537.1992249095. The cubic root of 1643264521 is about 1180.0556616949.

Adding to 1643264521 its reverse (1254623461), we get a palindrome (2897887982).

The spelling of 1643264521 in words is "one billion, six hundred forty-three million, two hundred sixty-four thousand, five hundred twenty-one".