20001000021 has 16 divisors (see below), whose sum is σ = 28241057664. Its totient is φ = 12547713024.

The previous prime is 20001000013. The next prime is 20001000049. The reversal of 20001000021 is 12000010002.

It is a happy number.

It is not a de Polignac number, because 20001000021 - 2³ = 20001000013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20000999973 and 20001000009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20001000001) 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, 350520 + ... + 403566.

It is an arithmetic number, because the mean of its divisors is an integer number (1765066104).

Almost surely, 2^20001000021 is an apocalyptic number.

It is an amenable number.

20001000021 is a deficient number, since it is larger than the sum of its proper divisors (8240057643).

20001000021 is a wasteful number, since it uses less digits than its factorization.

20001000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60460.

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

Adding to 20001000021 its reverse (12000010002), we get a palindrome (32001010023).

The spelling of 20001000021 in words is "twenty billion, one million, twenty-one", and thus it is an aban number and an uban number.