21641615 has 8 divisors (see below), whose sum is σ = 26009520. Its totient is φ = 17286912.

The previous prime is 21641611. The next prime is 21641671. The reversal of 21641615 is 51614612.

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

It is a cyclic number.

It is not a de Polignac number, because 21641615 - 2² = 21641611 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21641611) 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 7 ways as a sum of consecutive naturals, for example, 767 + ... + 6623.

It is an arithmetic number, because the mean of its divisors is an integer number (3251190).

Almost surely, 2^21641615 is an apocalyptic number.

21641615 is a deficient number, since it is larger than the sum of its proper divisors (4367905).

21641615 is an equidigital number, since it uses as much as digits as its factorization.

21641615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6601.

The product of its digits is 1440, while the sum is 26.

The square root of 21641615 is about 4652.0549222897. The cubic root of 21641615 is about 278.6740668718.

The spelling of 21641615 in words is "twenty-one million, six hundred forty-one thousand, six hundred fifteen".