21642815 has 8 divisors (see below), whose sum is σ = 26461728. Its totient is φ = 16987360.

The previous prime is 21642799. The next prime is 21642833. The reversal of 21642815 is 51824612.

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

It is not a de Polignac number, because 21642815 - 2⁴ = 21642799 is a prime.

It is a super-2 number, since 2×21642815² = 936822882248450, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40571 + ... + 41100.

It is an arithmetic number, because the mean of its divisors is an integer number (3307716).

Almost surely, 2^21642815 is an apocalyptic number.

21642815 is a deficient number, since it is larger than the sum of its proper divisors (4818913).

21642815 is an equidigital number, since it uses as much as digits as its factorization.

21642815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81729.

The product of its digits is 3840, while the sum is 29.

The square root of 21642815 is about 4652.1838957634. The cubic root of 21642815 is about 278.6792174840.

The spelling of 21642815 in words is "twenty-one million, six hundred forty-two thousand, eight hundred fifteen".