1921202021 has 2 divisors, whose sum is σ = 1921202022. Its totient is φ = 1921202020.

The previous prime is 1921201999. The next prime is 1921202039. The reversal of 1921202021 is 1202021291.

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., 1839208996 + 81993025 = 42886^2 + 9055^2 .

It is a cyclic number.

It is not a de Polignac number, because 1921202021 - 2¹⁰ = 1921200997 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1921201984 and 1921202002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1921202071) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 960601010 + 960601011.

It is an arithmetic number, because the mean of its divisors is an integer number (960601011).

Almost surely, 2^1921202021 is an apocalyptic number.

It is an amenable number.

1921202021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1921202021 is an equidigital number, since it uses as much as digits as its factorization.

1921202021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 1921202021 is about 43831.5185796705. The cubic root of 1921202021 is about 1243.1523204071.

The spelling of 1921202021 in words is "one billion, nine hundred twenty-one million, two hundred two thousand, twenty-one".