21000002000 has 80 divisors (see below), whose sum is σ = 52529115600. Its totient is φ = 8110323200.

The previous prime is 21000001987. The next prime is 21000002003. The reversal of 21000002000 is 20000012.

It can be written as a sum of positive squares in 8 ways, for example, as 6039776656 + 14960225344 = 77716^2 + 122312^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (5).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000002003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 123035 + ... + 239034.

It is an arithmetic number, because the mean of its divisors is an integer number (656613945).

Almost surely, 2^21000002000 is an apocalyptic number.

21000002000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000002000 is an abundant number, since it is smaller than the sum of its proper divisors (31529113600).

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

21000002000 is a wasteful number, since it uses less digits than its factorization.

21000002000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 362121 (or 362105 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 5.

Adding to 21000002000 its reverse (20000012), we get a palindrome (21020002012).

The spelling of 21000002000 in words is "twenty-one billion, two thousand".