21221000020 has 48 divisors (see below), whose sum is σ = 48896483328. Its totient is φ = 7672108160.

The previous prime is 21220999973. The next prime is 21221000027. The reversal of 21221000020 is 2000012212.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21220999970 and 21221000006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221000027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 240724 + ... + 316843.

It is an arithmetic number, because the mean of its divisors is an integer number (1018676736).

Almost surely, 2^21221000020 is an apocalyptic number.

21221000020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221000020 is an abundant number, since it is smaller than the sum of its proper divisors (27675483308).

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

21221000020 is a wasteful number, since it uses less digits than its factorization.

21221000020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 557760 (or 557758 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21221000020 its reverse (2000012212), we get a palindrome (23221012232).

The spelling of 21221000020 in words is "twenty-one billion, two hundred twenty-one million, twenty", and thus it is an aban number.