21006491982 has 48 divisors (see below), whose sum is σ = 49020124032. Its totient is φ = 5983694640.

The previous prime is 21006491971. The next prime is 21006492007. The reversal of 21006491982 is 28919460012.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10618 + ... + 205245.

It is an arithmetic number, because the mean of its divisors is an integer number (1021252584).

Almost surely, 2^21006491982 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21006491982, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24510062016).

21006491982 is an abundant number, since it is smaller than the sum of its proper divisors (28013632050).

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

21006491982 is a wasteful number, since it uses less digits than its factorization.

21006491982 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216213 (or 216206 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 42.

The spelling of 21006491982 in words is "twenty-one billion, six million, four hundred ninety-one thousand, nine hundred eighty-two".