1221115657 has 2 divisors, whose sum is σ = 1221115658. Its totient is φ = 1221115656.

The previous prime is 1221115633. The next prime is 1221115667. The reversal of 1221115657 is 7565111221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1004319481 + 216796176 = 31691^2 + 14724^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221115657 - 2¹¹ = 1221113609 is a prime.

It is a super-2 number, since 2×1221115657² = 2982246895541083298, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1221115607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610557828 + 610557829.

It is an arithmetic number, because the mean of its divisors is an integer number (610557829).

Almost surely, 2^1221115657 is an apocalyptic number.

It is an amenable number.

1221115657 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221115657 is an equidigital number, since it uses as much as digits as its factorization.

1221115657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4200, while the sum is 31.

The square root of 1221115657 is about 34944.4653271444. The cubic root of 1221115657 is about 1068.8553447589.

Adding to 1221115657 its reverse (7565111221), we get a palindrome (8786226878).

The spelling of 1221115657 in words is "one billion, two hundred twenty-one million, one hundred fifteen thousand, six hundred fifty-seven".