21928647 has 8 divisors (see below), whose sum is σ = 31487344. Its totient is φ = 13494528.

The previous prime is 21928639. The next prime is 21928663. The reversal of 21928647 is 74682912.

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

It is not a de Polignac number, because 21928647 - 2³ = 21928639 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39), and also a Moran number because the ratio is a prime number: 562273 = 21928647 / (2 + 1 + 9 + 2 + 8 + 6 + 4 + 7).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21928447) 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, 281098 + ... + 281175.

It is an arithmetic number, because the mean of its divisors is an integer number (3935918).

Almost surely, 2^21928647 is an apocalyptic number.

21928647 is a deficient number, since it is larger than the sum of its proper divisors (9558697).

21928647 is a wasteful number, since it uses less digits than its factorization.

21928647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 562289.

The product of its digits is 48384, while the sum is 39.

The square root of 21928647 is about 4682.8033270681. The cubic root of 21928647 is about 279.9006748043.

The spelling of 21928647 in words is "twenty-one million, nine hundred twenty-eight thousand, six hundred forty-seven".