21001221012120 has 64 divisors (see below), whose sum is σ = 63069774253920. Its totient is φ = 5594449050624.

The previous prime is 21001221012119. The next prime is 21001221012133. The reversal of 21001221012120 is 2121012210012.

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 21001221012120.

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, 91706299 + ... + 91935018.

Almost surely, 2^{21001221012120} is an apocalyptic number.

21001221012120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001221012120 is an abundant number, since it is smaller than the sum of its proper divisors (42068553241800).

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

21001221012120 is a wasteful number, since it uses less digits than its factorization.

21001221012120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183642284 (or 183642280 counting only the distinct ones).

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

Adding to 21001221012120 its reverse (2121012210012), we get a palindrome (23122233222132).

The spelling of 21001221012120 in words is "twenty-one trillion, one billion, two hundred twenty-one million, twelve thousand, one hundred twenty".