21457903 has 4 divisors (see below), whose sum is σ = 21956968. Its totient is φ = 20958840.

The previous prime is 21457871. The next prime is 21457939. The reversal of 21457903 is 30975412.

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

It is a cyclic number.

It is not a de Polignac number, because 21457903 - 2⁵ = 21457871 is a prime.

It is a super-3 number, since 3×21457903³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21457963) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 249468 + ... + 249553.

It is an arithmetic number, because the mean of its divisors is an integer number (5489242).

Almost surely, 2^21457903 is an apocalyptic number.

21457903 is a deficient number, since it is larger than the sum of its proper divisors (499065).

21457903 is an equidigital number, since it uses as much as digits as its factorization.

21457903 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499064.

The product of its (nonzero) digits is 7560, while the sum is 31.

The square root of 21457903 is about 4632.2675872622. The cubic root of 21457903 is about 277.8832860649.

The spelling of 21457903 in words is "twenty-one million, four hundred fifty-seven thousand, nine hundred three".