1221222001921 has 2 divisors, whose sum is σ = 1221222001922. Its totient is φ = 1221222001920.

The previous prime is 1221222001919. The next prime is 1221222001949. The reversal of 1221222001921 is 1291002221221.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 749671978896 + 471550023025 = 865836^2 + 686695^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221222001921 - 2¹ = 1221222001919 is a prime.

Together with 1221222001919, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1221222007921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610611000960 + 610611000961.

It is an arithmetic number, because the mean of its divisors is an integer number (610611000961).

Almost surely, 2^{1221222001921} is an apocalyptic number.

It is an amenable number.

1221222001921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221222001921 is an equidigital number, since it uses as much as digits as its factorization.

1221222001921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 25.

The spelling of 1221222001921 in words is "one trillion, two hundred twenty-one billion, two hundred twenty-two million, one thousand, nine hundred twenty-one".