21557449 has 3 divisors (see below), whose sum is σ = 21562093. Its totient is φ = 21552806.

The previous prime is 21557447. The next prime is 21557453. The reversal of 21557449 is 94475512.

The square root of 21557449 is 4643.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 21557449 - 2¹ = 21557447 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21557447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2322 + ... + 6964.

Almost surely, 2^21557449 is an apocalyptic number.

21557449 is the 4643-rd square number.

21557449 is the 2322-nd centered octagonal number.

It is an amenable number.

21557449 is a deficient number, since it is larger than the sum of its proper divisors (4644).

21557449 is an frugal number, since it uses more digits than its factorization.

21557449 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9286 (or 4643 counting only the distinct ones).

The product of its digits is 50400, while the sum is 37.

The cubic root of 21557449 is about 278.3123354983.

It can be divided in two parts, 2155 and 7449, that added together give a square (9604 = 98²).

The spelling of 21557449 in words is "twenty-one million, five hundred fifty-seven thousand, four hundred forty-nine".