21387685540 has 96 divisors (see below), whose sum is σ = 52557603840. Its totient is φ = 7239974400.

The previous prime is 21387685511. The next prime is 21387685573. The reversal of 21387685540 is 4558678312.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 83310 + ... + 222970.

It is an arithmetic number, because the mean of its divisors is an integer number (547475040).

Almost surely, 2^21387685540 is an apocalyptic number.

21387685540 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 21387685540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26278801920).

21387685540 is an abundant number, since it is smaller than the sum of its proper divisors (31169918300).

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

21387685540 is a wasteful number, since it uses less digits than its factorization.

21387685540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139733 (or 139731 counting only the distinct ones).

The product of its (nonzero) digits is 1612800, while the sum is 49.

The spelling of 21387685540 in words is "twenty-one billion, three hundred eighty-seven million, six hundred eighty-five thousand, five hundred forty".