21400393 has 16 divisors (see below), whose sum is σ = 25608960. Its totient is φ = 17499456.

The previous prime is 21400387. The next prime is 21400397. The reversal of 21400393 is 39300412.

It is a cyclic number.

It is not a de Polignac number, because 21400393 - 2⁵ = 21400361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21400397) 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 in 15 ways as a sum of consecutive naturals, for example, 12948 + ... + 14506.

It is an arithmetic number, because the mean of its divisors is an integer number (1600560).

Almost surely, 2^21400393 is an apocalyptic number.

It is an amenable number.

21400393 is a deficient number, since it is larger than the sum of its proper divisors (4208567).

21400393 is a wasteful number, since it uses less digits than its factorization.

21400393 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1656.

The product of its (nonzero) digits is 648, while the sum is 22.

The square root of 21400393 is about 4626.0558794723. The cubic root of 21400393 is about 277.6348093739.

The spelling of 21400393 in words is "twenty-one million, four hundred thousand, three hundred ninety-three".