21342157 has 4 divisors (see below), whose sum is σ = 22597596. Its totient is φ = 20086720.

The previous prime is 21342143. The next prime is 21342161. The reversal of 21342157 is 75124312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10458756 + 10883401 = 3234^2 + 3299^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21342157 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 (21342257) 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, 627694 + ... + 627727.

It is an arithmetic number, because the mean of its divisors is an integer number (5649399).

Almost surely, 2^21342157 is an apocalyptic number.

It is an amenable number.

21342157 is a deficient number, since it is larger than the sum of its proper divisors (1255439).

21342157 is a wasteful number, since it uses less digits than its factorization.

21342157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1255438.

The product of its digits is 1680, while the sum is 25.

The square root of 21342157 is about 4619.7572447045. The cubic root of 21342157 is about 277.3827418995.

Adding to 21342157 its reverse (75124312), we get a palindrome (96466469).

The spelling of 21342157 in words is "twenty-one million, three hundred forty-two thousand, one hundred fifty-seven".