21712155 has 64 divisors (see below), whose sum is σ = 39398400. Its totient is φ = 10160640.

The previous prime is 21712153. The next prime is 21712169. The reversal of 21712155 is 55121712.

It is not a de Polignac number, because 21712155 - 2¹ = 21712153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21712151) 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 63 ways as a sum of consecutive naturals, for example, 305770 + ... + 305840.

It is an arithmetic number, because the mean of its divisors is an integer number (615600).

Almost surely, 2^21712155 is an apocalyptic number.

21712155 is a deficient number, since it is larger than the sum of its proper divisors (17686245).

21712155 is a wasteful number, since it uses less digits than its factorization.

21712155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164.

The product of its digits is 700, while the sum is 24.

The square root of 21712155 is about 4659.6303501458. The cubic root of 21712155 is about 278.9765142549.

Adding to 21712155 its reverse (55121712), we get a palindrome (76833867).

The spelling of 21712155 in words is "twenty-one million, seven hundred twelve thousand, one hundred fifty-five".