21000012102 has 128 divisors (see below), whose sum is σ = 48306585600. Its totient is φ = 6759855648.

The previous prime is 21000012083. The next prime is 21000012107. The reversal of 21000012102 is 20121000012.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000012107) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 44967673 + ... + 44968139.

It is an arithmetic number, because the mean of its divisors is an integer number (377395200).

Almost surely, 2^21000012102 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21000012102, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24153292800).

21000012102 is an abundant number, since it is smaller than the sum of its proper divisors (27306573498).

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

21000012102 is a wasteful number, since it uses less digits than its factorization.

21000012102 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 767 (or 761 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21000012102 its reverse (20121000012), we get a palindrome (41121012114).

The spelling of 21000012102 in words is "twenty-one billion, twelve thousand, one hundred two".