21730137 has 32 divisors (see below), whose sum is σ = 34984320. Its totient is φ = 11828160.

The previous prime is 21730133. The next prime is 21730139. The reversal of 21730137 is 73103712.

It is not a de Polignac number, because 21730137 - 2² = 21730133 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21730133) 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 in 31 ways as a sum of consecutive naturals, for example, 587283 + ... + 587319.

It is an arithmetic number, because the mean of its divisors is an integer number (1093260).

Almost surely, 2^21730137 is an apocalyptic number.

It is an amenable number.

21730137 is a deficient number, since it is larger than the sum of its proper divisors (13254183).

21730137 is an equidigital number, since it uses as much as digits as its factorization.

21730137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138 (or 64 counting only the distinct ones).

The product of its (nonzero) digits is 882, while the sum is 24.

The square root of 21730137 is about 4661.5595029990. The cubic root of 21730137 is about 279.0535090905.

Adding to 21730137 its reverse (73103712), we get a palindrome (94833849).

The spelling of 21730137 in words is "twenty-one million, seven hundred thirty thousand, one hundred thirty-seven".