212121021 has 16 divisors (see below), whose sum is σ = 330750464. Its totient is φ = 118392624.

The previous prime is 212120983. The next prime is 212121023. The reversal of 212121021 is 120121212.

It is not a de Polignac number, because 212121021 - 2⁶ = 212120957 is a prime.

It is a super-3 number, since 3×212121021³ (a number of 26 digits) contains 333 as substring.

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 = 212120988 and 212121006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (212121023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 116551 + ... + 118356.

It is an arithmetic number, because the mean of its divisors is an integer number (20671904).

Almost surely, 2^212121021 is an apocalyptic number.

212121021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

212121021 is a deficient number, since it is larger than the sum of its proper divisors (118629443).

212121021 is a wasteful number, since it uses less digits than its factorization.

212121021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 234960.

The product of its (nonzero) digits is 16, while the sum is 12.

The square root of 212121021 is about 14564.3750638330. The cubic root of 212121021 is about 596.3866357925.

Adding to 212121021 its reverse (120121212), we get a palindrome (332242233).

The spelling of 212121021 in words is "two hundred twelve million, one hundred twenty-one thousand, twenty-one".