21511724040 has 160 divisors (see below), whose sum is σ = 72360783000. Its totient is φ = 5731900416.

The previous prime is 21511724029. The next prime is 21511724051. The reversal of 21511724040 is 4042711512.

21511724040 is a `hidden beast` number, since 2 + 1 + 511 + 72 + 40 + 40 = 666.

It is an interprime number because it is at equal distance from previous prime (21511724029) and next prime (21511724051).

It can be written as a sum of positive squares in 4 ways, for example, as 14229149796 + 7282574244 = 119286^2 + 85338^2 .

It is a super-2 number, since 2×21511724040² (a number of 21 digits) contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 21511723995 and 21511724013.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 6701956 + ... + 6705164.

Almost surely, 2^21511724040 is an apocalyptic number.

21511724040 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 21511724040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36180391500).

21511724040 is an abundant number, since it is smaller than the sum of its proper divisors (50849058960).

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

21511724040 is a wasteful number, since it uses less digits than its factorization.

21511724040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5301 (or 5288 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The spelling of 21511724040 in words is "twenty-one billion, five hundred eleven million, seven hundred twenty-four thousand, forty".