65631221 has 2 divisors, whose sum is σ = 65631222. Its totient is φ = 65631220.

The previous prime is 65631217. The next prime is 65631227. The reversal of 65631221 is 12213656.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 40780996 + 24850225 = 6386^2 + 4985^2 .

It is a cyclic number.

It is not a de Polignac number, because 65631221 - 2² = 65631217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (65631227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32815610 + 32815611.

It is an arithmetic number, because the mean of its divisors is an integer number (32815611).

Almost surely, 2^65631221 is an apocalyptic number.

It is an amenable number.

65631221 is a deficient number, since it is larger than the sum of its proper divisors (1).

65631221 is an equidigital number, since it uses as much as digits as its factorization.

65631221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 26.

The square root of 65631221 is about 8101.3098323666. The cubic root of 65631221 is about 403.3699066775.

Adding to 65631221 its reverse (12213656), we get a palindrome (77844877).

The spelling of 65631221 in words is "sixty-five million, six hundred thirty-one thousand, two hundred twenty-one".