21121212021 has 32 divisors (see below), whose sum is σ = 35049934080. Its totient is φ = 11015668224.

The previous prime is 21121212019. The next prime is 21121212031. The reversal of 21121212021 is 12021212112.

It is not a de Polignac number, because 21121212021 - 2¹ = 21121212019 is a prime.

It is a super-2 number, since 2×21121212021² (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 (21121212031) 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, 410350 + ... + 458943.

It is an arithmetic number, because the mean of its divisors is an integer number (1095310440).

Almost surely, 2^21121212021 is an apocalyptic number.

21121212021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21121212021 is a deficient number, since it is larger than the sum of its proper divisors (13928722059).

21121212021 is a wasteful number, since it uses less digits than its factorization.

21121212021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 869405.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21121212021 its reverse (12021212112), we get a palindrome (33142424133).

Subtracting from 21121212021 its reverse (12021212112), we obtain a palindrome (9099999909).

The spelling of 21121212021 in words is "twenty-one billion, one hundred twenty-one million, two hundred twelve thousand, twenty-one".