21566157 has 8 divisors (see below), whose sum is σ = 30005184. Its totient is φ = 13752288.

The previous prime is 21566147. The next prime is 21566189. The reversal of 21566157 is 75166512.

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

It is not a de Polignac number, because 21566157 - 2⁴ = 21566141 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21566117) 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 7 ways as a sum of consecutive naturals, for example, 156208 + ... + 156345.

It is an arithmetic number, because the mean of its divisors is an integer number (3750648).

Almost surely, 2^21566157 is an apocalyptic number.

It is an amenable number.

21566157 is a deficient number, since it is larger than the sum of its proper divisors (8439027).

21566157 is a wasteful number, since it uses less digits than its factorization.

21566157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312579.

The product of its digits is 12600, while the sum is 33.

The square root of 21566157 is about 4643.9376610803. The cubic root of 21566157 is about 278.3498046435.

The spelling of 21566157 in words is "twenty-one million, five hundred sixty-six thousand, one hundred fifty-seven".