21678403 has 4 divisors (see below), whose sum is σ = 21816640. Its totient is φ = 21540168.

The previous prime is 21678401. The next prime is 21678427. The reversal of 21678403 is 30487612.

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 21678403 - 2¹ = 21678401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21678401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68883 + ... + 69196.

It is an arithmetic number, because the mean of its divisors is an integer number (5454160).

Almost surely, 2^21678403 is an apocalyptic number.

21678403 is a deficient number, since it is larger than the sum of its proper divisors (138237).

21678403 is a wasteful number, since it uses less digits than its factorization.

21678403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138236.

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 21678403 is about 4656.0071950116. The cubic root of 21678403 is about 278.8318810044.

The spelling of 21678403 in words is "twenty-one million, six hundred seventy-eight thousand, four hundred three".