20021100021 has 32 divisors (see below), whose sum is σ = 32271854720. Its totient is φ = 12193638912.

The previous prime is 20021100019. The next prime is 20021100023. The reversal of 20021100021 is 12000112002.

It is an interprime number because it is at equal distance from previous prime (20021100019) and next prime (20021100023).

It is not a de Polignac number, because 20021100021 - 2¹ = 20021100019 is a prime.

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

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 = 20021099976 and 20021100012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20021100023) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 259975 + ... + 328068.

It is an arithmetic number, because the mean of its divisors is an integer number (1008495460).

Almost surely, 2^20021100021 is an apocalyptic number.

It is an amenable number.

20021100021 is a deficient number, since it is larger than the sum of its proper divisors (12250754699).

20021100021 is a wasteful number, since it uses less digits than its factorization.

20021100021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 588162 (or 588156 counting only the distinct ones).

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

Adding to 20021100021 its reverse (12000112002), we get a palindrome (32021212023).

The spelling of 20021100021 in words is "twenty billion, twenty-one million, one hundred thousand, twenty-one".