21147557 has 8 divisors (see below), whose sum is σ = 22317120. Its totient is φ = 19998880.

The previous prime is 21147523. The next prime is 21147559. The reversal of 21147557 is 75574112.

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 21147557 - 2⁶ = 21147493 is a prime.

It is a Duffinian number.

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147559) 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 7 ways as a sum of consecutive naturals, for example, 3119 + ... + 7212.

It is an arithmetic number, because the mean of its divisors is an integer number (2789640).

Almost surely, 2^21147557 is an apocalyptic number.

It is an amenable number.

21147557 is a deficient number, since it is larger than the sum of its proper divisors (1169563).

21147557 is a wasteful number, since it uses less digits than its factorization.

21147557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10443.

The product of its digits is 9800, while the sum is 32.

The square root of 21147557 is about 4598.6473011093. The cubic root of 21147557 is about 276.5370982468.

The spelling of 21147557 in words is "twenty-one million, one hundred forty-seven thousand, five hundred fifty-seven".