1221210212021 has 2 divisors, whose sum is σ = 1221210212022. Its totient is φ = 1221210212020.

The previous prime is 1221210212009. The next prime is 1221210212051. The reversal of 1221210212021 is 1202120121221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1207306500625 + 13903711396 = 1098775^2 + 117914^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221210212021 - 2²⁶ = 1221143103157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221210212051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610605106010 + 610605106011.

It is an arithmetic number, because the mean of its divisors is an integer number (610605106011).

Almost surely, 2^{1221210212021} is an apocalyptic number.

It is an amenable number.

1221210212021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221210212021 is an equidigital number, since it uses as much as digits as its factorization.

1221210212021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 1221210212021 its reverse (1202120121221), we get a palindrome (2423330333242).

The spelling of 1221210212021 in words is "one trillion, two hundred twenty-one billion, two hundred ten million, two hundred twelve thousand, twenty-one".