21551361984 has 112 divisors (see below), whose sum is σ = 63686273440. Its totient is φ = 7146455040.

The previous prime is 21551361967. The next prime is 21551361989. The reversal of 21551361984 is 48916315512.

It is a happy number.

21551361984 is a `hidden beast` number, since 2 + 1 + 551 + 3 + 6 + 1 + 98 + 4 = 666.

It is a super-2 number, since 2×21551361984² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551361989) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 301194 + ... + 365814.

Almost surely, 2^21551361984 is an apocalyptic number.

21551361984 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 21551361984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31843136720).

21551361984 is an abundant number, since it is smaller than the sum of its proper divisors (42134911456).

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

21551361984 is a wasteful number, since it uses less digits than its factorization.

21551361984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64835 (or 64819 counting only the distinct ones).

The product of its digits is 259200, while the sum is 45.

The spelling of 21551361984 in words is "twenty-one billion, five hundred fifty-one million, three hundred sixty-one thousand, nine hundred eighty-four".