21599781840 has 960 divisors, whose sum is σ = 94108262400. Its totient is φ = 4457576448.

The previous prime is 21599781829. The next prime is 21599781857. The reversal of 21599781840 is 4818799512.

It is a happy number.

21599781840 is a `hidden beast` number, since 2 + 1 + 599 + 7 + 8 + 1 + 8 + 40 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 201867067 + ... + 201867173.

It is an arithmetic number, because the mean of its divisors is an integer number (98029440).

Almost surely, 2^21599781840 is an apocalyptic number.

21599781840 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 21599781840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47054131200).

21599781840 is an abundant number, since it is smaller than the sum of its proper divisors (72508480560).

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

21599781840 is a wasteful number, since it uses less digits than its factorization.

21599781840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241 (or 216 counting only the distinct ones).

The product of its (nonzero) digits is 1451520, while the sum is 54.

The spelling of 21599781840 in words is "twenty-one billion, five hundred ninety-nine million, seven hundred eighty-one thousand, eight hundred forty".