1021220021 has 2 divisors, whose sum is σ = 1021220022. Its totient is φ = 1021220020.

The previous prime is 1021219957. The next prime is 1021220027. The reversal of 1021220021 is 1200221201.

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., 923308996 + 97911025 = 30386^2 + 9895^2 .

It is a cyclic number.

It is not a de Polignac number, because 1021220021 - 2⁶ = 1021219957 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1021219984 and 1021220011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1021220027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510610010 + 510610011.

It is an arithmetic number, because the mean of its divisors is an integer number (510610011).

Almost surely, 2^1021220021 is an apocalyptic number.

It is an amenable number.

1021220021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1021220021 is an equidigital number, since it uses as much as digits as its factorization.

1021220021 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 1021220021 is about 31956.5333069781. The cubic root of 1021220021 is about 1007.0238897975.

Adding to 1021220021 its reverse (1200221201), we get a palindrome (2221441222).

The spelling of 1021220021 in words is "one billion, twenty-one million, two hundred twenty thousand, twenty-one".