21651472 has 20 divisors (see below), whose sum is σ = 44417916. Its totient is φ = 10188800.

The previous prime is 21651449. The next prime is 21651473. The reversal of 21651472 is 27415612.

It can be written as a sum of positive squares in 2 ways, for example, as 5779216 + 15872256 = 2404^2 + 3984^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21651472.

It is not an unprimeable number, because it can be changed into a prime (21651473) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39529 + ... + 40072.

Almost surely, 2^21651472 is an apocalyptic number.

It is an amenable number.

21651472 is an abundant number, since it is smaller than the sum of its proper divisors (22766444).

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

21651472 is a wasteful number, since it uses less digits than its factorization.

21651472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79626 (or 79620 counting only the distinct ones).

The product of its digits is 3360, while the sum is 28.

The square root of 21651472 is about 4653.1142259781. The cubic root of 21651472 is about 278.7163692192.

The spelling of 21651472 in words is "twenty-one million, six hundred fifty-one thousand, four hundred seventy-two".