21053557 has 8 divisors (see below), whose sum is σ = 24837632. Its totient is φ = 17463600.

The previous prime is 21053537. The next prime is 21053563. The reversal of 21053557 is 75535012.

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

It is a de Polignac number, because none of the positive numbers 2^k-21053557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21053537) 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, 48294 + ... + 48727.

It is an arithmetic number, because the mean of its divisors is an integer number (3104704).

Almost surely, 2^21053557 is an apocalyptic number.

It is an amenable number.

21053557 is a deficient number, since it is larger than the sum of its proper divisors (3784075).

21053557 is an equidigital number, since it uses as much as digits as its factorization.

21053557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97059.

The product of its (nonzero) digits is 5250, while the sum is 28.

The square root of 21053557 is about 4588.4155217242. The cubic root of 21053557 is about 276.1267577454.

Adding to 21053557 its reverse (75535012), we get a palindrome (96588569).

The spelling of 21053557 in words is "twenty-one million, fifty-three thousand, five hundred fifty-seven".