21403936 has 12 divisors (see below), whose sum is σ = 42139062. Its totient is φ = 10701952.

The previous prime is 21403931. The next prime is 21403973. The reversal of 21403936 is 63930412.

It can be written as a sum of positive squares in only one way, i.e., 21344400 + 59536 = 4620^2 + 244^2 .

It is not an unprimeable number, because it can be changed into a prime (21403931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334405 + ... + 334468.

Almost surely, 2^21403936 is an apocalyptic number.

It is an amenable number.

21403936 is a deficient number, since it is larger than the sum of its proper divisors (20735126).

21403936 is an equidigital number, since it uses as much as digits as its factorization.

21403936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668883 (or 668875 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 28.

The square root of 21403936 is about 4626.4388032265. The cubic root of 21403936 is about 277.6501300560.

The spelling of 21403936 in words is "twenty-one million, four hundred three thousand, nine hundred thirty-six".