21128406552 has 64 divisors (see below), whose sum is σ = 64025481600. Its totient is φ = 6402546720.

The previous prime is 21128406529. The next prime is 21128406569. The reversal of 21128406552 is 25560482112.

21128406552 is a `hidden beast` number, since 21 + 1 + 2 + 84 + 0 + 6 + 552 = 666.

It is a super-3 number, since 3×21128406552³ (a number of 32 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4443838 + ... + 4448589.

It is an arithmetic number, because the mean of its divisors is an integer number (1000398150).

Almost surely, 2^21128406552 is an apocalyptic number.

21128406552 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21128406552 is an abundant number, since it is smaller than the sum of its proper divisors (42897075048).

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

21128406552 is a wasteful number, since it uses less digits than its factorization.

21128406552 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8892453 (or 8892443 counting only the distinct ones).

The product of its (nonzero) digits is 38400, while the sum is 36.

Adding to 21128406552 its reverse (25560482112), we get a palindrome (46688888664).

The spelling of 21128406552 in words is "twenty-one billion, one hundred twenty-eight million, four hundred six thousand, five hundred fifty-two".