21307456 has 21 divisors (see below), whose sum is σ = 42355389. Its totient is φ = 10635264.

The previous prime is 21307441. The next prime is 21307457. The reversal of 21307456 is 65470312.

The square root of 21307456 is 4616.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 21160000 + 147456 = 4600^2 + 384^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21307457) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 36640 + ... + 37216.

Almost surely, 2^21307456 is an apocalyptic number.

21307456 is the 4616-th square number.

It is an amenable number.

21307456 is a deficient number, since it is larger than the sum of its proper divisors (21047933).

21307456 is an frugal number, since it uses more digits than its factorization.

21307456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1166 (or 579 counting only the distinct ones).

The product of its (nonzero) digits is 5040, while the sum is 28.

The cubic root of 21307456 is about 277.2323247378.

Adding to 21307456 its reverse (65470312), we get a palindrome (86777768).

The spelling of 21307456 in words is "twenty-one million, three hundred seven thousand, four hundred fifty-six".