21812947 has 8 divisors (see below), whose sum is σ = 24512544. Its totient is φ = 19259328.

The previous prime is 21812939. The next prime is 21812951. The reversal of 21812947 is 74921812.

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 21812947 - 2³ = 21812939 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21812977) 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, 36178 + ... + 36775.

It is an arithmetic number, because the mean of its divisors is an integer number (3064068).

Almost surely, 2^21812947 is an apocalyptic number.

21812947 is a deficient number, since it is larger than the sum of its proper divisors (2699597).

21812947 is a wasteful number, since it uses less digits than its factorization.

21812947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72989.

The product of its digits is 8064, while the sum is 34.

The square root of 21812947 is about 4670.4332775450. The cubic root of 21812947 is about 279.4075355275.

The spelling of 21812947 in words is "twenty-one million, eight hundred twelve thousand, nine hundred forty-seven".