21201212020 has 24 divisors (see below), whose sum is σ = 45149626368. Its totient is φ = 8361040800.

The previous prime is 21201212009. The next prime is 21201212027. The reversal of 21201212020 is 2021210212.

It is a happy number.

It is a super-2 number, since 2×21201212020² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201212027) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7463796 + ... + 7466635.

It is an arithmetic number, because the mean of its divisors is an integer number (1881234432).

Almost surely, 2^21201212020 is an apocalyptic number.

21201212020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21201212020 is an abundant number, since it is smaller than the sum of its proper divisors (23948414348).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21201212020 is a wasteful number, since it uses less digits than its factorization.

21201212020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14930511 (or 14930509 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21201212020 its reverse (2021210212), we get a palindrome (23222422232).

The spelling of 21201212020 in words is "twenty-one billion, two hundred one million, two hundred twelve thousand, twenty".