21400457 has 4 divisors (see below), whose sum is σ = 23046660. Its totient is φ = 19754256.

The previous prime is 21400453. The next prime is 21400459. The reversal of 21400457 is 75400412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14661241 + 6739216 = 3829^2 + 2596^2 .

It is a cyclic number.

It is not a de Polignac number, because 21400457 - 2² = 21400453 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21400451) 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 3 ways as a sum of consecutive naturals, for example, 823082 + ... + 823107.

It is an arithmetic number, because the mean of its divisors is an integer number (5761665).

Almost surely, 2^21400457 is an apocalyptic number.

It is an amenable number.

21400457 is a deficient number, since it is larger than the sum of its proper divisors (1646203).

21400457 is a wasteful number, since it uses less digits than its factorization.

21400457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1646202.

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21400457 is about 4626.0627968068. The cubic root of 21400457 is about 277.6350861385.

Adding to 21400457 its reverse (75400412), we get a palindrome (96800869).

The spelling of 21400457 in words is "twenty-one million, four hundred thousand, four hundred fifty-seven".