21537016344 has 128 divisors (see below), whose sum is σ = 65145600000. Its totient is φ = 6566603904.

The previous prime is 21537016343. The next prime is 21537016349. The reversal of 21537016344 is 44361073512.

21537016344 is a `hidden beast` number, since 2 + 15 + 3 + 7 + 0 + 1 + 634 + 4 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 21537016299 and 21537016308.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21537016343) 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, 28537 + ... + 209495.

It is an arithmetic number, because the mean of its divisors is an integer number (508950000).

Almost surely, 2^21537016344 is an apocalyptic number.

21537016344 is a gapful number since it is divisible by the number (24) 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 21537016344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32572800000).

21537016344 is an abundant number, since it is smaller than the sum of its proper divisors (43608583656).

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

21537016344 is a wasteful number, since it uses less digits than its factorization.

21537016344 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181022 (or 181012 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 36.

Adding to 21537016344 its reverse (44361073512), we get a palindrome (65898089856).

The spelling of 21537016344 in words is "twenty-one billion, five hundred thirty-seven million, sixteen thousand, three hundred forty-four".