21031457 has 2 divisors, whose sum is σ = 21031458. Its totient is φ = 21031456.

The previous prime is 21031433. The next prime is 21031463. The reversal of 21031457 is 75413012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16638241 + 4393216 = 4079^2 + 2096^2 .

It is a cyclic number.

It is not a de Polignac number, because 21031457 - 2⁶ = 21031393 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21031477) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515728 + 10515729.

It is an arithmetic number, because the mean of its divisors is an integer number (10515729).

Almost surely, 2^21031457 is an apocalyptic number.

It is an amenable number.

21031457 is a deficient number, since it is larger than the sum of its proper divisors (1).

21031457 is an equidigital number, since it uses as much as digits as its factorization.

21031457 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21031457 is about 4586.0066506711. The cubic root of 21031457 is about 276.0301068117.

Adding to 21031457 its reverse (75413012), we get a palindrome (96444469).

The spelling of 21031457 in words is "twenty-one million, thirty-one thousand, four hundred fifty-seven".