21232157 has 2 divisors, whose sum is σ = 21232158. Its totient is φ = 21232156.

The previous prime is 21232121. The next prime is 21232181. The reversal of 21232157 is 75123212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20693401 + 538756 = 4549^2 + 734^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21232157 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21232187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10616078 + 10616079.

It is an arithmetic number, because the mean of its divisors is an integer number (10616079).

Almost surely, 2^21232157 is an apocalyptic number.

It is an amenable number.

21232157 is a deficient number, since it is larger than the sum of its proper divisors (1).

21232157 is an equidigital number, since it uses as much as digits as its factorization.

21232157 is an evil number, because the sum of its binary digits is even.

The product of its digits is 840, while the sum is 23.

The square root of 21232157 is about 4607.8364771333. The cubic root of 21232157 is about 276.9053663274.

Adding to 21232157 its reverse (75123212), we get a palindrome (96355369).

The spelling of 21232157 in words is "twenty-one million, two hundred thirty-two thousand, one hundred fifty-seven".