21726464 has 18 divisors (see below), whose sum is σ = 43368570. Its totient is φ = 10863104.

The previous prime is 21726461. The next prime is 21726473. The reversal of 21726464 is 46462712.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 640000 = 4592^2 + 800^2 .

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a self number, because there is not a number n which added to its sum of digits gives 21726464.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21726461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42179 + ... + 42690.

It is an arithmetic number, because the mean of its divisors is an integer number (2409365).

Almost surely, 2^21726464 is an apocalyptic number.

It is an amenable number.

21726464 is a deficient number, since it is larger than the sum of its proper divisors (21642106).

21726464 is an frugal number, since it uses more digits than its factorization.

21726464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84885 (or 84871 counting only the distinct ones).

The product of its digits is 16128, while the sum is 32.

The square root of 21726464 is about 4661.1655194812. The cubic root of 21726464 is about 279.0377855925.

The spelling of 21726464 in words is "twenty-one million, seven hundred twenty-six thousand, four hundred sixty-four".