21561337 has 16 divisors (see below), whose sum is σ = 25833472. Its totient is φ = 17606160.

The previous prime is 21561329. The next prime is 21561341. The reversal of 21561337 is 73316512.

It is a cyclic number.

It is not a de Polignac number, because 21561337 - 2³ = 21561329 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21561347) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13798 + ... + 15280.

It is an arithmetic number, because the mean of its divisors is an integer number (1614592).

Almost surely, 2^21561337 is an apocalyptic number.

It is an amenable number.

21561337 is a deficient number, since it is larger than the sum of its proper divisors (4272135).

21561337 is a wasteful number, since it uses less digits than its factorization.

21561337 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1588.

The product of its digits is 3780, while the sum is 28.

The square root of 21561337 is about 4643.4186759326. The cubic root of 21561337 is about 278.3290661933.

Adding to 21561337 its reverse (73316512), we get a palindrome (94877849).

The spelling of 21561337 in words is "twenty-one million, five hundred sixty-one thousand, three hundred thirty-seven".