64521221 has 4 divisors (see below), whose sum is σ = 64579500. Its totient is φ = 64462944.

The previous prime is 64521217. The next prime is 64521227. The reversal of 64521221 is 12212546.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12212546 = 2 ⋅6106273.

It can be written as a sum of positive squares in 2 ways, for example, as 3290596 + 61230625 = 1814^2 + 7825^2 .

It is a cyclic number.

It is not a de Polignac number, because 64521221 - 2² = 64521217 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 (64521227) 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, 27446 + ... + 29703.

It is an arithmetic number, because the mean of its divisors is an integer number (16144875).

Almost surely, 2^64521221 is an apocalyptic number.

It is an amenable number.

64521221 is a deficient number, since it is larger than the sum of its proper divisors (58279).

64521221 is a wasteful number, since it uses less digits than its factorization.

64521221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58278.

The product of its digits is 960, while the sum is 23.

The square root of 64521221 is about 8032.5102552066. The cubic root of 64521221 is about 401.0829425261.

Adding to 64521221 its reverse (12212546), we get a palindrome (76733767).

The spelling of 64521221 in words is "sixty-four million, five hundred twenty-one thousand, two hundred twenty-one".