71651221 has 2 divisors, whose sum is σ = 71651222. Its totient is φ = 71651220.

The previous prime is 71651219. The next prime is 71651227. The reversal of 71651221 is 12215617.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54552996 + 17098225 = 7386^2 + 4135^2 .

It is a cyclic number.

It is not a de Polignac number, because 71651221 - 2¹ = 71651219 is a prime.

Together with 71651219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71651227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35825610 + 35825611.

It is an arithmetic number, because the mean of its divisors is an integer number (35825611).

Almost surely, 2^71651221 is an apocalyptic number.

It is an amenable number.

71651221 is a deficient number, since it is larger than the sum of its proper divisors (1).

71651221 is an equidigital number, since it uses as much as digits as its factorization.

71651221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 840, while the sum is 25.

The square root of 71651221 is about 8464.7044248456. The cubic root of 71651221 is about 415.3439274073.

Adding to 71651221 its reverse (12215617), we get a palindrome (83866838).

The spelling of 71651221 in words is "seventy-one million, six hundred fifty-one thousand, two hundred twenty-one".