1001220021 has 24 divisors (see below), whose sum is σ = 1504767264. Its totient is φ = 665256240.

The previous prime is 1001220019. The next prime is 1001220043. The reversal of 1001220021 is 1200221001.

It is not a de Polignac number, because 1001220021 - 2¹ = 1001220019 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1001219985 and 1001220012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1001220001) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 67891 + ... + 81311.

It is an arithmetic number, because the mean of its divisors is an integer number (62698636).

Almost surely, 2^1001220021 is an apocalyptic number.

It is an amenable number.

1001220021 is a deficient number, since it is larger than the sum of its proper divisors (503547243).

1001220021 is an equidigital number, since it uses as much as digits as its factorization.

1001220021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13743 (or 13731 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 1001220021 is about 31642.0609474162. The cubic root of 1001220021 is about 1000.4065083952.

Adding to 1001220021 its reverse (1200221001), we get a palindrome (2201441022).

The spelling of 1001220021 in words is "one billion, one million, two hundred twenty thousand, twenty-one".