21671517 has 16 divisors (see below), whose sum is σ = 33443840. Its totient is φ = 12226032.

The previous prime is 21671513. The next prime is 21671521. The reversal of 21671517 is 71517612.

It is an interprime number because it is at equal distance from previous prime (21671513) and next prime (21671521).

It is not a de Polignac number, because 21671517 - 2² = 21671513 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 (21671513) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4873 + ... + 8190.

It is an arithmetic number, because the mean of its divisors is an integer number (2090240).

Almost surely, 2^21671517 is an apocalyptic number.

It is an amenable number.

21671517 is a deficient number, since it is larger than the sum of its proper divisors (11772323).

21671517 is a wasteful number, since it uses less digits than its factorization.

21671517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13152.

The product of its digits is 2940, while the sum is 30.

The square root of 21671517 is about 4655.2676614777. The cubic root of 21671517 is about 278.8023548493.

The spelling of 21671517 in words is "twenty-one million, six hundred seventy-one thousand, five hundred seventeen".