21172715 has 8 divisors (see below), whose sum is σ = 25438848. Its totient is φ = 16917120.

The previous prime is 21172709. The next prime is 21172717. The reversal of 21172715 is 51727112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21172715 - 2⁶ = 21172651 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21172717) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2819 + ... + 7091.

It is an arithmetic number, because the mean of its divisors is an integer number (3179856).

Almost surely, 2^21172715 is an apocalyptic number.

21172715 is a deficient number, since it is larger than the sum of its proper divisors (4266133).

21172715 is an equidigital number, since it uses as much as digits as its factorization.

21172715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5269.

The product of its digits is 980, while the sum is 26.

The square root of 21172715 is about 4601.3818576597. The cubic root of 21172715 is about 276.6467147432.

Adding to 21172715 its reverse (51727112), we get a palindrome (72899827).

The spelling of 21172715 in words is "twenty-one million, one hundred seventy-two thousand, seven hundred fifteen".