21278723 has 8 divisors (see below), whose sum is σ = 21626880. Its totient is φ = 20933640.

The previous prime is 21278711. The next prime is 21278773. The reversal of 21278723 is 32787212.

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 21278723 - 2⁶ = 21278659 is a prime.

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

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21278723.

It is not an unprimeable number, because it can be changed into a prime (21278773) 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, 15998 + ... + 17276.

It is an arithmetic number, because the mean of its divisors is an integer number (2703360).

Almost surely, 2^21278723 is an apocalyptic number.

21278723 is a deficient number, since it is larger than the sum of its proper divisors (348157).

21278723 is a wasteful number, since it uses less digits than its factorization.

21278723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1537.

The product of its digits is 9408, while the sum is 32.

The square root of 21278723 is about 4612.8866233629. The cubic root of 21278723 is about 277.1076532042.

The spelling of 21278723 in words is "twenty-one million, two hundred seventy-eight thousand, seven hundred twenty-three".