21557973 has 8 divisors (see below), whose sum is σ = 28811200. Its totient is φ = 14338368.

The previous prime is 21557971. The next prime is 21557983. The reversal of 21557973 is 37975512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21557973 - 2¹ = 21557971 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 (21557971) 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, 6868 + ... + 9501.

It is an arithmetic number, because the mean of its divisors is an integer number (3601400).

Almost surely, 2^21557973 is an apocalyptic number.

It is an amenable number.

21557973 is a deficient number, since it is larger than the sum of its proper divisors (7253227).

21557973 is a wasteful number, since it uses less digits than its factorization.

21557973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16811.

The product of its digits is 66150, while the sum is 39.

The square root of 21557973 is about 4643.0564286900. The cubic root of 21557973 is about 278.3145904726.

The spelling of 21557973 in words is "twenty-one million, five hundred fifty-seven thousand, nine hundred seventy-three".