21712161 has 16 divisors (see below), whose sum is σ = 30320640. Its totient is φ = 13794000.

The previous prime is 21712153. The next prime is 21712169. The reversal of 21712161 is 16121712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21712153) and next prime (21712169).

It is not a de Polignac number, because 21712161 - 2³ = 21712153 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21712169) 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 in 15 ways as a sum of consecutive naturals, for example, 28536 + ... + 29286.

It is an arithmetic number, because the mean of its divisors is an integer number (1895040).

Almost surely, 2^21712161 is an apocalyptic number.

It is an amenable number.

21712161 is a deficient number, since it is larger than the sum of its proper divisors (8608479).

21712161 is a wasteful number, since it uses less digits than its factorization.

21712161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1196.

The product of its digits is 168, while the sum is 21.

The square root of 21712161 is about 4659.6309939737. The cubic root of 21712161 is about 278.9765399526.

Adding to 21712161 its reverse (16121712), we get a palindrome (37833873).

The spelling of 21712161 in words is "twenty-one million, seven hundred twelve thousand, one hundred sixty-one".