1221816949 has 2 divisors, whose sum is σ = 1221816950. Its totient is φ = 1221816948.

The previous prime is 1221816929. The next prime is 1221816961. The reversal of 1221816949 is 9496181221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 786802500 + 435014449 = 28050^2 + 20857^2 .

It is an emirp because it is prime and its reverse (9496181221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221816949 - 2⁵ = 1221816917 is a prime.

It is a super-3 number, since 3×1221816949³ (a number of 28 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221816929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610908474 + 610908475.

It is an arithmetic number, because the mean of its divisors is an integer number (610908475).

Almost surely, 2^1221816949 is an apocalyptic number.

It is an amenable number.

1221816949 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221816949 is an equidigital number, since it uses as much as digits as its factorization.

1221816949 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 43.

The square root of 1221816949 is about 34954.4982656024. The cubic root of 1221816949 is about 1069.0599216823.

The spelling of 1221816949 in words is "one billion, two hundred twenty-one million, eight hundred sixteen thousand, nine hundred forty-nine".