21027391020 has 120 divisors (see below), whose sum is σ = 66003715008. Its totient is φ = 5603904000.

The previous prime is 21027391009. The next prime is 21027391051. The reversal of 21027391020 is 2019372012.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 3805860 + ... + 3811380.

Almost surely, 2^21027391020 is an apocalyptic number.

21027391020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21027391020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33001857504).

21027391020 is an abundant number, since it is smaller than the sum of its proper divisors (44976323988).

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

21027391020 is a wasteful number, since it uses less digits than its factorization.

21027391020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7893 (or 7882 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The spelling of 21027391020 in words is "twenty-one billion, twenty-seven million, three hundred ninety-one thousand, twenty".