21212102640 has 80 divisors (see below), whose sum is σ = 65929494528. Its totient is φ = 5641767168.

The previous prime is 21212102629. The next prime is 21212102657. The reversal of 21212102640 is 4620121212.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-3 number, since 3×21212102640³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23464 + ... + 207303.

Almost surely, 2^21212102640 is an apocalyptic number.

21212102640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21212102640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32964747264).

21212102640 is an abundant number, since it is smaller than the sum of its proper divisors (44717391888).

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

21212102640 is a wasteful number, since it uses less digits than its factorization.

21212102640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231166 (or 231160 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

Adding to 21212102640 its reverse (4620121212), we get a palindrome (25832223852).

The spelling of 21212102640 in words is "twenty-one billion, two hundred twelve million, one hundred two thousand, six hundred forty".