21211212210 has 64 divisors (see below), whose sum is σ = 53785814400. Its totient is φ = 5338662912.

The previous prime is 21211212173. The next prime is 21211212233. The reversal of 21211212210 is 1221211212.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21211212210.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 84162 + ... + 222498.

It is an arithmetic number, because the mean of its divisors is an integer number (840403350).

Almost surely, 2^21211212210 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21211212210, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26892907200).

21211212210 is an abundant number, since it is smaller than the sum of its proper divisors (32574602190).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21211212210 is a wasteful number, since it uses less digits than its factorization.

21211212210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138635.

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

Adding to 21211212210 its reverse (1221211212), we get a palindrome (22432423422).

The spelling of 21211212210 in words is "twenty-one billion, two hundred eleven million, two hundred twelve thousand, two hundred ten".