21210121210 has 16 divisors (see below), whose sum is σ = 39494709000. Its totient is φ = 8191494976.

The previous prime is 21210121187. The next prime is 21210121223. The reversal of 21210121210 is 1212101212.

21210121210 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in 4 ways, for example, as 16640226009 + 4569895201 = 128997^2 + 67601^2 .

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36568885 + ... + 36569464.

Almost surely, 2^21210121210 is an apocalyptic number.

21210121210 is a deficient number, since it is larger than the sum of its proper divisors (18284587790).

21210121210 is a wasteful number, since it uses less digits than its factorization.

21210121210 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73138385.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21210121210 its reverse (1212101212), we get a palindrome (22422222422).

The spelling of 21210121210 in words is "twenty-one billion, two hundred ten million, one hundred twenty-one thousand, two hundred ten".