21008211840 has 1280 divisors, whose sum is σ = 98814988800. Its totient is φ = 4120657920.

The previous prime is 21008211823. The next prime is 21008211863. The reversal of 21008211840 is 4811280012.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 75841782 + ... + 75842058.

It is an arithmetic number, because the mean of its divisors is an integer number (77199210).

Almost surely, 2^21008211840 is an apocalyptic number.

21008211840 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 21008211840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49407494400).

21008211840 is an abundant number, since it is smaller than the sum of its proper divisors (77806776960).

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

21008211840 is a wasteful number, since it uses less digits than its factorization.

21008211840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345 (or 324 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 27.

Adding to 21008211840 its reverse (4811280012), we get a palindrome (25819491852).

The spelling of 21008211840 in words is "twenty-one billion, eight million, two hundred eleven thousand, eight hundred forty".