21611671 has 4 divisors (see below), whose sum is σ = 22114312. Its totient is φ = 21109032.

The previous prime is 21611669. The next prime is 21611687. The reversal of 21611671 is 17611612.

It is a happy number.

21611671 is nontrivially palindromic in base 15.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21611671 - 2¹ = 21611669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21611621) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 251256 + ... + 251341.

It is an arithmetic number, because the mean of its divisors is an integer number (5528578).

Almost surely, 2^21611671 is an apocalyptic number.

21611671 is a deficient number, since it is larger than the sum of its proper divisors (502641).

21611671 is an equidigital number, since it uses as much as digits as its factorization.

21611671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 502640.

The product of its digits is 504, while the sum is 25.

The square root of 21611671 is about 4648.8354455713. The cubic root of 21611671 is about 278.5454802292.

The spelling of 21611671 in words is "twenty-one million, six hundred eleven thousand, six hundred seventy-one".