21001000100020 has 48 divisors (see below), whose sum is σ = 46696724762688. Its totient is φ = 7906193953280.

The previous prime is 21001000099949. The next prime is 21001000100057. The reversal of 21001000100020 is 2000100010012.

It is a junction number, because it is equal to n+sod(n) for n = 21001000099976 and 21001000100012.

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, 68991555 + ... + 69295285.

It is an arithmetic number, because the mean of its divisors is an integer number (972848432556).

Almost surely, 2^{21001000100020} is an apocalyptic number.

21001000100020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001000100020 is an abundant number, since it is smaller than the sum of its proper divisors (25695724662668).

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

21001000100020 is a wasteful number, since it uses less digits than its factorization.

21001000100020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 507120 (or 507118 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 21001000100020 its reverse (2000100010012), we get a palindrome (23001100110032).

The spelling of 21001000100020 in words is "twenty-one trillion, one billion, one hundred thousand, twenty".