21417157 has 4 divisors (see below), whose sum is σ = 21493120. Its totient is φ = 21341196.

The previous prime is 21417131. The next prime is 21417169. The reversal of 21417157 is 75171412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21417157 is a prime.

It is a super-2 number, since 2×21417157² = 917389227925298, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21417107) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37557 + ... + 38122.

It is an arithmetic number, because the mean of its divisors is an integer number (5373280).

Almost surely, 2^21417157 is an apocalyptic number.

It is an amenable number.

21417157 is a deficient number, since it is larger than the sum of its proper divisors (75963).

21417157 is an equidigital number, since it uses as much as digits as its factorization.

21417157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75962.

The product of its digits is 1960, while the sum is 28.

The square root of 21417157 is about 4627.8674354394. The cubic root of 21417157 is about 277.7072855377.

Adding to 21417157 its reverse (75171412), we get a palindrome (96588569).

It can be divided in two parts, 214 and 17157, that added together give a palindrome (17371).

The spelling of 21417157 in words is "twenty-one million, four hundred seventeen thousand, one hundred fifty-seven".