21212012021 has 16 divisors (see below), whose sum is σ = 22894332480. Its totient is φ = 19581676800.

The previous prime is 21212011969. The next prime is 21212012023. The reversal of 21212012021 is 12021021212.

It is a cyclic number.

It is not a de Polignac number, because 21212012021 - 2¹⁰ = 21212010997 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21212011987 and 21212012005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212012023) 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, 125990 + ... + 241448.

It is an arithmetic number, because the mean of its divisors is an integer number (1430895780).

Almost surely, 2^21212012021 is an apocalyptic number.

It is an amenable number.

21212012021 is a deficient number, since it is larger than the sum of its proper divisors (1682320459).

21212012021 is a wasteful number, since it uses less digits than its factorization.

21212012021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115684.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21212012021 its reverse (12021021212), we get a palindrome (33233033233).

The spelling of 21212012021 in words is "twenty-one billion, two hundred twelve million, twelve thousand, twenty-one".