21457557 has 12 divisors (see below), whose sum is σ = 33812064. Its totient is φ = 13004520.

The previous prime is 21457523. The next prime is 21457603. The reversal of 21457557 is 75575412.

It is not a de Polignac number, because 21457557 - 2⁶ = 21457493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21457507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 108273 + ... + 108470.

It is an arithmetic number, because the mean of its divisors is an integer number (2817672).

Almost surely, 2^21457557 is an apocalyptic number.

It is an amenable number.

21457557 is a deficient number, since it is larger than the sum of its proper divisors (12354507).

21457557 is a wasteful number, since it uses less digits than its factorization.

21457557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216760 (or 216757 counting only the distinct ones).

The product of its digits is 49000, while the sum is 36.

The square root of 21457557 is about 4632.2302403918. The cubic root of 21457557 is about 277.8817924717.

The spelling of 21457557 in words is "twenty-one million, four hundred fifty-seven thousand, five hundred fifty-seven".