21181621500 has 240 divisors, whose sum is σ = 74423084736. Its totient is φ = 5213808000.

The previous prime is 21181621481. The next prime is 21181621501. The reversal of 21181621500 is 512618112.

21181621500 is a `hidden beast` number, since 21 + 1 + 81 + 62 + 1 + 500 = 666.

It is a super-2 number, since 2×21181621500² (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 congruent number.

It is not an unprimeable number, because it can be changed into a prime (21181621501) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 506385 + ... + 546615.

Almost surely, 2^21181621500 is an apocalyptic number.

21181621500 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 21181621500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37211542368).

21181621500 is an abundant number, since it is smaller than the sum of its proper divisors (53241463236).

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

21181621500 is a wasteful number, since it uses less digits than its factorization.

21181621500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40275 (or 40254 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 27.

The spelling of 21181621500 in words is "twenty-one billion, one hundred eighty-one million, six hundred twenty-one thousand, five hundred".