20100000021 has 16 divisors (see below), whose sum is σ = 27910224000. Its totient is φ = 12851091008.

The previous prime is 20099999981. The next prime is 20100000047. The reversal of 20100000021 is 12000000102.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 20100000021 - 2⁶ = 20099999957 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20099999955 and 20100000009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20100000121) 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, 762321 + ... + 788246.

It is an arithmetic number, because the mean of its divisors is an integer number (1744389000).

Almost surely, 2^20100000021 is an apocalyptic number.

It is an amenable number.

20100000021 is a deficient number, since it is larger than the sum of its proper divisors (7810223979).

20100000021 is a wasteful number, since it uses less digits than its factorization.

20100000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1550748.

The product of its (nonzero) digits is 4, while the sum is 6.

Adding to 20100000021 its reverse (12000000102), we get a palindrome (32100000123).

The spelling of 20100000021 in words is "twenty billion, one hundred million, twenty-one", and thus it is an aban number.