21500137 has 2 divisors, whose sum is σ = 21500138. Its totient is φ = 21500136.

The previous prime is 21500111. The next prime is 21500161. The reversal of 21500137 is 73100512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16410601 + 5089536 = 4051^2 + 2256^2 .

It is a cyclic number.

It is not a de Polignac number, because 21500137 - 2¹⁹ = 20975849 is a prime.

It is not a weakly prime, because it can be changed into another prime (21500177) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10750068 + 10750069.

It is an arithmetic number, because the mean of its divisors is an integer number (10750069).

Almost surely, 2^21500137 is an apocalyptic number.

It is an amenable number.

21500137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21500137 is an equidigital number, since it uses as much as digits as its factorization.

21500137 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 210, while the sum is 19.

The square root of 21500137 is about 4636.8240208142. The cubic root of 21500137 is about 278.0654789433.

Adding to 21500137 its reverse (73100512), we get a palindrome (94600649).

The spelling of 21500137 in words is "twenty-one million, five hundred thousand, one hundred thirty-seven".