21368947 has 4 divisors (see below), whose sum is σ = 21639520. Its totient is φ = 21098376.

The previous prime is 21368927. The next prime is 21368953. The reversal of 21368947 is 74986312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21368947 - 2¹⁵ = 21336179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21368927) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 135168 + ... + 135325.

It is an arithmetic number, because the mean of its divisors is an integer number (5409880).

Almost surely, 2^21368947 is an apocalyptic number.

21368947 is a deficient number, since it is larger than the sum of its proper divisors (270573).

21368947 is an equidigital number, since it uses as much as digits as its factorization.

21368947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 270572.

The product of its digits is 72576, while the sum is 40.

The square root of 21368947 is about 4622.6558383682. The cubic root of 21368947 is about 277.4987560478.

The spelling of 21368947 in words is "twenty-one million, three hundred sixty-eight thousand, nine hundred forty-seven".