21211212121 has 16 divisors (see below), whose sum is σ = 23241778560. Its totient is φ = 19197809280.

The previous prime is 21211212109. The next prime is 21211212133. The reversal of 21211212121 is 12121211212.

It is an interprime number because it is at equal distance from previous prime (21211212109) and next prime (21211212133).

It is a cyclic number.

It is not a de Polignac number, because 21211212121 - 2¹⁹ = 21210687833 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21211212095 and 21211212104.

It is not an unprimeable number, because it can be changed into a prime (21011212121) 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, 5625925 + ... + 5629693.

It is an arithmetic number, because the mean of its divisors is an integer number (1452611160).

Almost surely, 2^21211212121 is an apocalyptic number.

It is an amenable number.

21211212121 is a deficient number, since it is larger than the sum of its proper divisors (2030566439).

21211212121 is a wasteful number, since it uses less digits than its factorization.

21211212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5904.

The product of its digits is 32, while the sum is 16.

Adding to 21211212121 its reverse (12121211212), we get a palindrome (33332423333).

Subtracting from 21211212121 its reverse (12121211212), we obtain a palindrome (9090000909).

It can be divided in two parts, 21211212 and 121, that multiplied together give a palindrome (2566556652).

The spelling of 21211212121 in words is "twenty-one billion, two hundred eleven million, two hundred twelve thousand, one hundred twenty-one".