21747157 has 8 divisors (see below), whose sum is σ = 22393400. Its totient is φ = 21104064.

The previous prime is 21747149. The next prime is 21747163. The reversal of 21747157 is 75174712.

It can be written as a sum of positive squares in 4 ways, for example, as 4157521 + 17589636 = 2039^2 + 4194^2 .

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 21747157 - 2³ = 21747149 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 (21747107) 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, 25819 + ... + 26647.

It is an arithmetic number, because the mean of its divisors is an integer number (2799175).

Almost surely, 2^21747157 is an apocalyptic number.

It is an amenable number.

21747157 is a deficient number, since it is larger than the sum of its proper divisors (646243).

21747157 is an equidigital number, since it uses as much as digits as its factorization.

21747157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1575.

The product of its digits is 13720, while the sum is 34.

The square root of 21747157 is about 4663.3847149897. The cubic root of 21747157 is about 279.1263457422.

It can be divided in two parts, 21747 and 157, that added together give a square (21904 = 148²).

The spelling of 21747157 in words is "twenty-one million, seven hundred forty-seven thousand, one hundred fifty-seven".