21987987840 has 1280 divisors, whose sum is σ = 99525888000. Its totient is φ = 4502863872.

The previous prime is 21987987797. The next prime is 21987987851. The reversal of 21987987840 is 4878978912.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 278328921 + ... + 278328999.

It is an arithmetic number, because the mean of its divisors is an integer number (77754600).

Almost surely, 2^21987987840 is an apocalyptic number.

21987987840 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 21987987840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49762944000).

21987987840 is an abundant number, since it is smaller than the sum of its proper divisors (77537900160).

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

21987987840 is a wasteful number, since it uses less digits than its factorization.

21987987840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189 (or 168 counting only the distinct ones).

The product of its (nonzero) digits is 16257024, while the sum is 63.

The spelling of 21987987840 in words is "twenty-one billion, nine hundred eighty-seven million, nine hundred eighty-seven thousand, eight hundred forty".