21155436240 has 80 divisors (see below), whose sum is σ = 65722632768. Its totient is φ = 5629339648.

The previous prime is 21155436233. The next prime is 21155436311. The reversal of 21155436240 is 4263455112.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent 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 15 ways as a sum of consecutive naturals, for example, 17704 + ... + 206456.

Almost surely, 2^21155436240 is an apocalyptic number.

21155436240 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 21155436240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32861316384).

21155436240 is an abundant number, since it is smaller than the sum of its proper divisors (44567196528).

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

21155436240 is a wasteful number, since it uses less digits than its factorization.

21155436240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189236 (or 189230 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 33.

The spelling of 21155436240 in words is "twenty-one billion, one hundred fifty-five million, four hundred thirty-six thousand, two hundred forty".