66401221 has 4 divisors (see below), whose sum is σ = 67392352. Its totient is φ = 65410092.

The previous prime is 66401191. The next prime is 66401227. The reversal of 66401221 is 12210466.

66401221 = 189² + 190² + ... + 590².

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66401221 - 2¹¹ = 66399173 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 66401192 and 66401201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66401227) 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, 495465 + ... + 495598.

It is an arithmetic number, because the mean of its divisors is an integer number (16848088).

Almost surely, 2^66401221 is an apocalyptic number.

It is an amenable number.

66401221 is a deficient number, since it is larger than the sum of its proper divisors (991131).

66401221 is an equidigital number, since it uses as much as digits as its factorization.

66401221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 991130.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 66401221 is about 8148.6944353068. The cubic root of 66401221 is about 404.9412524654.

Adding to 66401221 its reverse (12210466), we get a palindrome (78611687).

The spelling of 66401221 in words is "sixty-six million, four hundred one thousand, two hundred twenty-one".