21212421021 has 40 divisors (see below), whose sum is σ = 34592726784. Its totient is φ = 12846962880.

The previous prime is 21212420993. The next prime is 21212421023. The reversal of 21212421021 is 12012421212.

21212421021 is a `hidden beast` number, since 212 + 12 + 421 + 0 + 21 = 666.

It is not a de Polignac number, because 21212421021 - 2⁵ = 21212420989 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21212420985 and 21212421003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212421023) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1388601 + ... + 1403793.

Almost surely, 2^21212421021 is an apocalyptic number.

It is an amenable number.

21212421021 is a deficient number, since it is larger than the sum of its proper divisors (13380305763).

21212421021 is a wasteful number, since it uses less digits than its factorization.

21212421021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16783 (or 16774 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

Adding to 21212421021 its reverse (12012421212), we get a palindrome (33224842233).

The spelling of 21212421021 in words is "twenty-one billion, two hundred twelve million, four hundred twenty-one thousand, twenty-one".