21048557 has 4 divisors (see below), whose sum is σ = 21130716. Its totient is φ = 20966400.

The previous prime is 21048553. The next prime is 21048571. The reversal of 21048557 is 75584012.

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 20557156 + 491401 = 4534^2 + 701^2 .

It is a cyclic number.

It is not a de Polignac number, because 21048557 - 2² = 21048553 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 (21048553) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40694 + ... + 41207.

It is an arithmetic number, because the mean of its divisors is an integer number (5282679).

Almost surely, 2^21048557 is an apocalyptic number.

It is an amenable number.

21048557 is a deficient number, since it is larger than the sum of its proper divisors (82159).

21048557 is an equidigital number, since it uses as much as digits as its factorization.

21048557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82158.

The product of its (nonzero) digits is 11200, while the sum is 32.

The square root of 21048557 is about 4587.8706389784. The cubic root of 21048557 is about 276.1048969407.

The spelling of 21048557 in words is "twenty-one million, forty-eight thousand, five hundred fifty-seven".