20120021 has 4 divisors (see below), whose sum is σ = 20248332. Its totient is φ = 19991712.

The previous prime is 20119991. The next prime is 20120029. The reversal of 20120021 is 12002102.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10817521 + 9302500 = 3289^2 + 3050^2 .

It is a cyclic number.

It is not a de Polignac number, because 20120021 - 2¹⁴ = 20103637 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20119990 and 20120008.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20120029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63920 + ... + 64233.

It is an arithmetic number, because the mean of its divisors is an integer number (5062083).

Almost surely, 2^20120021 is an apocalyptic number.

It is an amenable number.

20120021 is a deficient number, since it is larger than the sum of its proper divisors (128311).

20120021 is a wasteful number, since it uses less digits than its factorization.

20120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128310.

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

The square root of 20120021 is about 4485.5346392599. The cubic root of 20120021 is about 271.9836576470.

Adding to 20120021 its reverse (12002102), we get a palindrome (32122123).

The spelling of 20120021 in words is "twenty million, one hundred twenty thousand, twenty-one".