21788712 has 144 divisors (see below), whose sum is σ = 67534740. Its totient is φ = 6336000.

The previous prime is 21788681. The next prime is 21788719.

It is a happy number.

21788712 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in 2 ways, for example, as 15163236 + 6625476 = 3894^2 + 2574^2 .

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

It is a zygodrome in base 3 and base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21788719) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 357162 + ... + 357222.

Almost surely, 2^21788712 is an apocalyptic number.

21788712 is a gapful number since it is divisible by the number (22) 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 21788712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33767370).

21788712 is an abundant number, since it is smaller than the sum of its proper divisors (45746028).

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

21788712 is a wasteful number, since it uses less digits than its factorization.

21788712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136 (or 118 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 21788712 is about 4667.8380434629. The cubic root of 21788712 is about 279.3040197738.

It can be divided in two parts, 21788 and 712, that added together give a square (22500 = 150²).

The spelling of 21788712 in words is "twenty-one million, seven hundred eighty-eight thousand, seven hundred twelve".