21172137 has 32 divisors (see below), whose sum is σ = 34713600. Its totient is φ = 11207808.

The previous prime is 21172133. The next prime is 21172139. The reversal of 21172137 is 73127112.

It is not a de Polignac number, because 21172137 - 2² = 21172133 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21172133) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 18189 + ... + 19317.

It is an arithmetic number, because the mean of its divisors is an integer number (1084800).

Almost surely, 2^21172137 is an apocalyptic number.

It is an amenable number.

21172137 is a deficient number, since it is larger than the sum of its proper divisors (13541463).

21172137 is a wasteful number, since it uses less digits than its factorization.

21172137 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1205.

The product of its digits is 588, while the sum is 24.

The square root of 21172137 is about 4601.3190500116. The cubic root of 21172137 is about 276.6441973010.

Adding to 21172137 its reverse (73127112), we get a palindrome (94299249).

The spelling of 21172137 in words is "twenty-one million, one hundred seventy-two thousand, one hundred thirty-seven".