21231757 has 2 divisors, whose sum is σ = 21231758. Its totient is φ = 21231756.

The previous prime is 21231731. The next prime is 21231761. The reversal of 21231757 is 75713212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18610596 + 2621161 = 4314^2 + 1619^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231757 - 2⁷ = 21231629 is a prime.

It is equal to p_1343638 and since 21231757 and 1343638 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21231767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615878 + 10615879.

It is an arithmetic number, because the mean of its divisors is an integer number (10615879).

Almost surely, 2^21231757 is an apocalyptic number.

It is an amenable number.

21231757 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231757 is an equidigital number, since it uses as much as digits as its factorization.

21231757 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21231757 is about 4607.7930726108. The cubic root of 21231757 is about 276.9036274109.

Adding to 21231757 its reverse (75713212), we get a palindrome (96944969).

The spelling of 21231757 in words is "twenty-one million, two hundred thirty-one thousand, seven hundred fifty-seven".