64661221 has 4 divisors (see below), whose sum is σ = 64684332. Its totient is φ = 64638112.

The previous prime is 64661203. The next prime is 64661249. The reversal of 64661221 is 12216646.

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 33189121 + 31472100 = 5761^2 + 5610^2 .

It is a cyclic number.

It is not a de Polignac number, because 64661221 - 2¹⁷ = 64530149 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 64661221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64661321) 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, 6670 + ... + 13183.

It is an arithmetic number, because the mean of its divisors is an integer number (16171083).

Almost surely, 2^64661221 is an apocalyptic number.

It is an amenable number.

64661221 is a deficient number, since it is larger than the sum of its proper divisors (23111).

64661221 is a wasteful number, since it uses less digits than its factorization.

64661221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23110.

The product of its digits is 3456, while the sum is 28.

The square root of 64661221 is about 8041.2201188626. The cubic root of 64661221 is about 401.3728267267.

Adding to 64661221 its reverse (12216646), we get a palindrome (76877867).

The spelling of 64661221 in words is "sixty-four million, six hundred sixty-one thousand, two hundred twenty-one".