21215867 has 8 divisors (see below), whose sum is σ = 22206624. Its totient is φ = 20230848.

The previous prime is 21215851. The next prime is 21215893. The reversal of 21215867 is 76851212.

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 21215867 - 2⁴ = 21215851 is a prime.

It is a super-2 number, since 2×21215867² = 900226025123378, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21215807) 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, 7343 + ... + 9815.

It is an arithmetic number, because the mean of its divisors is an integer number (2775828).

Almost surely, 2^21215867 is an apocalyptic number.

21215867 is a deficient number, since it is larger than the sum of its proper divisors (990757).

21215867 is a wasteful number, since it uses less digits than its factorization.

21215867 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2869.

The product of its digits is 6720, while the sum is 32.

The square root of 21215867 is about 4606.0684971025. The cubic root of 21215867 is about 276.8345312804.

The spelling of 21215867 in words is "twenty-one million, two hundred fifteen thousand, eight hundred sixty-seven".