1221404021 has 2 divisors, whose sum is σ = 1221404022. Its totient is φ = 1221404020.

The previous prime is 1221403987. The next prime is 1221404033. The reversal of 1221404021 is 1204041221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 900600100 + 320803921 = 30010^2 + 17911^2 .

It is an emirp because it is prime and its reverse (1204041221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221404021 - 2²² = 1217209717 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221404081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610702010 + 610702011.

It is an arithmetic number, because the mean of its divisors is an integer number (610702011).

Almost surely, 2^1221404021 is an apocalyptic number.

It is an amenable number.

1221404021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221404021 is an equidigital number, since it uses as much as digits as its factorization.

1221404021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 1221404021 is about 34948.5911160951. The cubic root of 1221404021 is about 1068.9394741484.

Adding to 1221404021 its reverse (1204041221), we get a palindrome (2425445242).

The spelling of 1221404021 in words is "one billion, two hundred twenty-one million, four hundred four thousand, twenty-one".