21143557 has 4 divisors (see below), whose sum is σ = 21192160. Its totient is φ = 21094956.

The previous prime is 21143537. The next prime is 21143569. The reversal of 21143557 is 75534112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21143557 is a prime.

It is a super-2 number, since 2×21143557² = 894100005224498, which contains 22 as substring.

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 (21143537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23643 + ... + 24520.

It is an arithmetic number, because the mean of its divisors is an integer number (5298040).

Almost surely, 2^21143557 is an apocalyptic number.

It is an amenable number.

21143557 is a deficient number, since it is larger than the sum of its proper divisors (48603).

21143557 is an equidigital number, since it uses as much as digits as its factorization.

21143557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48602.

The product of its digits is 4200, while the sum is 28.

The square root of 21143557 is about 4598.2123700412. The cubic root of 21143557 is about 276.5196617467.

Adding to 21143557 its reverse (75534112), we get a palindrome (96677669).

It can be divided in two parts, 2114 and 3557, that added together give a triangular number (5671 = T₁₀₆).

The spelling of 21143557 in words is "twenty-one million, one hundred forty-three thousand, five hundred fifty-seven".