21057137 has 2 divisors, whose sum is σ = 21057138. Its totient is φ = 21057136.

The previous prime is 21057131. The next prime is 21057151. The reversal of 21057137 is 73175012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11316496 + 9740641 = 3364^2 + 3121^2 .

It is a cyclic number.

It is not a de Polignac number, because 21057137 - 2¹² = 21053041 is a prime.

It is not a weakly prime, because it can be changed into another prime (21057131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10528568 + 10528569.

It is an arithmetic number, because the mean of its divisors is an integer number (10528569).

Almost surely, 2^21057137 is an apocalyptic number.

It is an amenable number.

21057137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21057137 is an equidigital number, since it uses as much as digits as its factorization.

21057137 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1470, while the sum is 26.

The square root of 21057137 is about 4588.8056180231. The cubic root of 21057137 is about 276.1424079555.

The spelling of 21057137 in words is "twenty-one million, fifty-seven thousand, one hundred thirty-seven".