21505388472 has 48 divisors (see below), whose sum is σ = 59198588280. Its totient is φ = 7050945600.

The previous prime is 21505388461. The next prime is 21505388477. The reversal of 21505388472 is 27488350512.

21505388472 is a `hidden beast` number, since 2 + 1 + 50 + 53 + 88 + 472 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505388477) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2443854 + ... + 2452637.

Almost surely, 2^21505388472 is an apocalyptic number.

It is an amenable number.

21505388472 is an abundant number, since it is smaller than the sum of its proper divisors (37693199808).

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

21505388472 is a wasteful number, since it uses less digits than its factorization.

21505388472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4896564 (or 4896557 counting only the distinct ones).

The product of its (nonzero) digits is 537600, while the sum is 45.

The spelling of 21505388472 in words is "twenty-one billion, five hundred five million, three hundred eighty-eight thousand, four hundred seventy-two".