1216526221 has 2 divisors, whose sum is σ = 1216526222. Its totient is φ = 1216526220.

The previous prime is 1216526173. The next prime is 1216526237. The reversal of 1216526221 is 1226256121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 625550121 + 590976100 = 25011^2 + 24310^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216526221 - 2¹³ = 1216518029 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1216526221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1216526261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608263110 + 608263111.

It is an arithmetic number, because the mean of its divisors is an integer number (608263111).

Almost surely, 2^1216526221 is an apocalyptic number.

It is an amenable number.

1216526221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216526221 is an equidigital number, since it uses as much as digits as its factorization.

1216526221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 28.

The square root of 1216526221 is about 34878.7359432649. The cubic root of 1216526221 is about 1067.5146031820.

The spelling of 1216526221 in words is "one billion, two hundred sixteen million, five hundred twenty-six thousand, two hundred twenty-one".