21054257 has 8 divisors (see below), whose sum is σ = 24091200. Its totient is φ = 18024624.

The previous prime is 21054247. The next prime is 21054259. The reversal of 21054257 is 75245012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21054257 - 2²⁰ = 20005681 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21054259) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7619 + ... + 10007.

It is an arithmetic number, because the mean of its divisors is an integer number (3011400).

Almost surely, 2^21054257 is an apocalyptic number.

It is an amenable number.

21054257 is a deficient number, since it is larger than the sum of its proper divisors (3036943).

21054257 is a wasteful number, since it uses less digits than its factorization.

21054257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3655.

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21054257 is about 4588.4918001452. The cubic root of 21054257 is about 276.1298179819.

Adding to 21054257 its reverse (75245012), we get a palindrome (96299269).

The spelling of 21054257 in words is "twenty-one million, fifty-four thousand, two hundred fifty-seven".