21723157 has 8 divisors (see below), whose sum is σ = 22579200. Its totient is φ = 20876880.

The previous prime is 21723113. The next prime is 21723167. The reversal of 21723157 is 75132712.

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 21723157 - 2⁷ = 21723029 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 (21723167) 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, 2268 + ... + 6970.

It is an arithmetic number, because the mean of its divisors is an integer number (2822400).

Almost surely, 2^21723157 is an apocalyptic number.

It is an amenable number.

21723157 is a deficient number, since it is larger than the sum of its proper divisors (856043).

21723157 is a wasteful number, since it uses less digits than its factorization.

21723157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4883.

The product of its digits is 2940, while the sum is 28.

The square root of 21723157 is about 4660.8107663796. The cubic root of 21723157 is about 279.0236273632.

Adding to 21723157 its reverse (75132712), we get a palindrome (96855869).

It can be divided in two parts, 2172 and 3157, that added together give a square (5329 = 73²).

The spelling of 21723157 in words is "twenty-one million, seven hundred twenty-three thousand, one hundred fifty-seven".