1221002021 has 2 divisors, whose sum is σ = 1221002022. Its totient is φ = 1221002020.

The previous prime is 1221002011. The next prime is 1221002023. The reversal of 1221002021 is 1202001221.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 731973025 + 489028996 = 27055^2 + 22114^2 .

It is an emirp because it is prime and its reverse (1202001221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221002021 - 2¹⁰ = 1221000997 is a prime.

Together with 1221002023, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 1221001993 and 1221002011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221002023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610501010 + 610501011.

It is an arithmetic number, because the mean of its divisors is an integer number (610501011).

Almost surely, 2^1221002021 is an apocalyptic number.

It is an amenable number.

1221002021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221002021 is an equidigital number, since it uses as much as digits as its factorization.

1221002021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 1221002021 is about 34942.8393379817. The cubic root of 1221002021 is about 1068.8221881361.

Adding to 1221002021 its reverse (1202001221), we get a palindrome (2423003242).

The spelling of 1221002021 in words is "one billion, two hundred twenty-one million, two thousand, twenty-one".