1001200021 has 4 divisors (see below), whose sum is σ = 1001613292. Its totient is φ = 1000786752.

The previous prime is 1001200019. The next prime is 1001200043. The reversal of 1001200021 is 1200021001.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1200021001 = 59 ⋅20339339.

It can be written as a sum of positive squares in 2 ways, for example, as 678602500 + 322597521 = 26050^2 + 17961^2 .

It is a cyclic number.

It is not a de Polignac number, because 1001200021 - 2¹ = 1001200019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1001199977 and 1001200013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1001204021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 202980 + ... + 207853.

It is an arithmetic number, because the mean of its divisors is an integer number (250403323).

Almost surely, 2^1001200021 is an apocalyptic number.

It is an amenable number.

1001200021 is a deficient number, since it is larger than the sum of its proper divisors (413271).

1001200021 is an equidigital number, since it uses as much as digits as its factorization.

1001200021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 413270.

The product of its (nonzero) digits is 4, while the sum is 7.

The square root of 1001200021 is about 31641.7449107978. The cubic root of 1001200021 is about 1000.3998471010.

Adding to 1001200021 its reverse (1200021001), we get a palindrome (2201221022).

The spelling of 1001200021 in words is "one billion, one million, two hundred thousand, twenty-one".