1220021021 has 4 divisors (see below), whose sum is σ = 1220110044. Its totient is φ = 1219932000.

The previous prime is 1220021009. The next prime is 1220021029. The reversal of 1220021021 is 1201200221.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1201200221 = 13 ⋅92400017.

It can be written as a sum of positive squares in 2 ways, for example, as 530380900 + 689640121 = 23030^2 + 26261^2 .

It is a cyclic number.

It is not a de Polignac number, because 1220021021 - 2⁶ = 1220020957 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1220020993 and 1220021011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1220021029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19130 + ... + 52971.

It is an arithmetic number, because the mean of its divisors is an integer number (305027511).

Almost surely, 2^1220021021 is an apocalyptic number.

It is an amenable number.

1220021021 is a deficient number, since it is larger than the sum of its proper divisors (89023).

1220021021 is an equidigital number, since it uses as much as digits as its factorization.

1220021021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89022.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 1220021021 is about 34928.7993065894. The cubic root of 1220021021 is about 1068.5358671528.

Adding to 1220021021 its reverse (1201200221), we get a palindrome (2421221242).

The spelling of 1220021021 in words is "one billion, two hundred twenty million, twenty-one thousand, twenty-one".