1221010219921 has 2 divisors, whose sum is σ = 1221010219922. Its totient is φ = 1221010219920.

The previous prime is 1221010219889. The next prime is 1221010220063. The reversal of 1221010219921 is 1299120101221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 970745149696 + 250265070225 = 985264^2 + 500265^2 .

It is an emirp because it is prime and its reverse (1299120101221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221010219921 - 2⁵ = 1221010219889 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221010229921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610505109960 + 610505109961.

It is an arithmetic number, because the mean of its divisors is an integer number (610505109961).

Almost surely, 2^{1221010219921} is an apocalyptic number.

It is an amenable number.

1221010219921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221010219921 is an equidigital number, since it uses as much as digits as its factorization.

1221010219921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 31.

The spelling of 1221010219921 in words is "one trillion, two hundred twenty-one billion, ten million, two hundred nineteen thousand, nine hundred twenty-one".