21557147 has 8 divisors (see below), whose sum is σ = 22126896. Its totient is φ = 20990592.

The previous prime is 21557143. The next prime is 21557177. The reversal of 21557147 is 74175512.

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

It is a cyclic number.

It is not a de Polignac number, because 21557147 - 2² = 21557143 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21557143) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19103 + ... + 20199.

It is an arithmetic number, because the mean of its divisors is an integer number (2765862).

Almost surely, 2^21557147 is an apocalyptic number.

21557147 is a deficient number, since it is larger than the sum of its proper divisors (569749).

21557147 is a wasteful number, since it uses less digits than its factorization.

21557147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1597.

The product of its digits is 9800, while the sum is 32.

The square root of 21557147 is about 4642.9674778099. The cubic root of 21557147 is about 278.3110358591.

The spelling of 21557147 in words is "twenty-one million, five hundred fifty-seven thousand, one hundred forty-seven".