21100001220 has 72 divisors (see below), whose sum is σ = 67371944640. Its totient is φ = 5330525760.

The previous prime is 21100001213. The next prime is 21100001227. The reversal of 21100001220 is 2210000112.

It is an interprime number because it is at equal distance from previous prime (21100001213) and next prime (21100001227).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is not an unprimeable number, because it can be changed into a prime (21100001227) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3081376 + ... + 3088215.

Almost surely, 2^21100001220 is an apocalyptic number.

21100001220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21100001220 is an abundant number, since it is smaller than the sum of its proper divisors (46271943420).

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

21100001220 is a wasteful number, since it uses less digits than its factorization.

21100001220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6169625 (or 6169620 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21100001220 its reverse (2210000112), we get a palindrome (23310001332).

The spelling of 21100001220 in words is "twenty-one billion, one hundred million, one thousand, two hundred twenty".