21400424 has 8 divisors (see below), whose sum is σ = 40125810. Its totient is φ = 10700208.

The previous prime is 21400417. The next prime is 21400429. The reversal of 21400424 is 42400412.

It can be written as a sum of positive squares in only one way, i.e., 20884900 + 515524 = 4570^2 + 718^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (21400429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1337519 + ... + 1337534.

Almost surely, 2^21400424 is an apocalyptic number.

It is an amenable number.

21400424 is a deficient number, since it is larger than the sum of its proper divisors (18725386).

21400424 is a wasteful number, since it uses less digits than its factorization.

21400424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2675059 (or 2675055 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 21400424 is about 4626.0592300575. The cubic root of 21400424 is about 277.6349434318.

Adding to 21400424 its reverse (42400412), we get a palindrome (63800836).

The spelling of 21400424 in words is "twenty-one million, four hundred thousand, four hundred twenty-four".