21537755428 has 96 divisors (see below), whose sum is σ = 45265651200. Its totient is φ = 8775782400.

The previous prime is 21537755411. The next prime is 21537755429. The reversal of 21537755428 is 82455773512.

It is not an unprimeable number, because it can be changed into a prime (21537755429) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7252728 + ... + 7255696.

It is an arithmetic number, because the mean of its divisors is an integer number (471517200).

Almost surely, 2^21537755428 is an apocalyptic number.

21537755428 is a gapful number since it is divisible by the number (28) 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 21537755428, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22632825600).

21537755428 is an abundant number, since it is smaller than the sum of its proper divisors (23727895772).

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

21537755428 is a wasteful number, since it uses less digits than its factorization.

21537755428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3181 (or 3179 counting only the distinct ones).

The product of its digits is 2352000, while the sum is 49.

The spelling of 21537755428 in words is "twenty-one billion, five hundred thirty-seven million, seven hundred fifty-five thousand, four hundred twenty-eight".