21647472 has 80 divisors (see below), whose sum is σ = 69733632. Its totient is φ = 5621760.

The previous prime is 21647471. The next prime is 21647503. The reversal of 21647472 is 27474612.

It is a super-2 number, since 2×21647472² = 937226087981568, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21647471) 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, 768 + ... + 6624.

Almost surely, 2^21647472 is an apocalyptic number.

21647472 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 21647472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34866816).

21647472 is an abundant number, since it is smaller than the sum of its proper divisors (48086160).

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

21647472 is a wasteful number, since it uses less digits than its factorization.

21647472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5886 (or 5880 counting only the distinct ones).

The product of its digits is 18816, while the sum is 33.

The square root of 21647472 is about 4652.6843864591. The cubic root of 21647472 is about 278.6992043486.

The spelling of 21647472 in words is "twenty-one million, six hundred forty-seven thousand, four hundred seventy-two".