21787272 has 64 divisors (see below), whose sum is σ = 65184000. Its totient is φ = 6702912.

The previous prime is 21787237. The next prime is 21787301. The reversal of 21787272 is 27278712.

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

It is a zygodrome in base 11.

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, 1072 + ... + 6687.

It is an arithmetic number, because the mean of its divisors is an integer number (1018500).

Almost surely, 2^21787272 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21787272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32592000).

21787272 is an abundant number, since it is smaller than the sum of its proper divisors (43396728).

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

21787272 is a wasteful number, since it uses less digits than its factorization.

21787272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7787 (or 7777 counting only the distinct ones).

The product of its digits is 21952, while the sum is 36.

The square root of 21787272 is about 4667.6837939175. The cubic root of 21787272 is about 279.2978666390.

The spelling of 21787272 in words is "twenty-one million, seven hundred eighty-seven thousand, two hundred seventy-two".