21042157 has 2 divisors, whose sum is σ = 21042158. Its totient is φ = 21042156.

The previous prime is 21042127. The next prime is 21042187. The reversal of 21042157 is 75124012.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21042127) and next prime (21042187).

It can be written as a sum of positive squares in only one way, i.e., 15594601 + 5447556 = 3949^2 + 2334^2 .

It is a cyclic number.

It is not a de Polignac number, because 21042157 - 2¹⁵ = 21009389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21042127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521078 + 10521079.

It is an arithmetic number, because the mean of its divisors is an integer number (10521079).

Almost surely, 2^21042157 is an apocalyptic number.

It is an amenable number.

21042157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21042157 is an equidigital number, since it uses as much as digits as its factorization.

21042157 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 21042157 is about 4587.1730946194. The cubic root of 21042157 is about 276.0769100583.

Adding to 21042157 its reverse (75124012), we get a palindrome (96166169).

The spelling of 21042157 in words is "twenty-one million, forty-two thousand, one hundred fifty-seven".