21021212121210 has 384 divisors, whose sum is σ = 65380030709760. Its totient is φ = 4584565440000.

The previous prime is 21021212121209. The next prime is 21021212121257. The reversal of 21021212121210 is 1212121212012.

21021212121210 is a `hidden beast` number, since 210 + 2 + 121 + 2 + 121 + 210 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 923957335 + ... + 923980085.

It is an arithmetic number, because the mean of its divisors is an integer number (170260496640).

Almost surely, 2^{21021212121210} is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21021212121210, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32690015354880).

21021212121210 is an abundant number, since it is smaller than the sum of its proper divisors (44358818588550).

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

21021212121210 is a wasteful number, since it uses less digits than its factorization.

21021212121210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23394 (or 23391 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

Adding to 21021212121210 its reverse (1212121212012), we get a palindrome (22233333333222).

The spelling of 21021212121210 in words is "twenty-one trillion, twenty-one billion, two hundred twelve million, one hundred twenty-one thousand, two hundred ten".