21004923 has 8 divisors (see below), whose sum is σ = 28465936. Its totient is φ = 13773600.

The previous prime is 21004913. The next prime is 21004931. The reversal of 21004923 is 32940012.

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

It is not a de Polignac number, because 21004923 - 2⁵ = 21004891 is a prime.

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 21004923.

It is not an unprimeable number, because it can be changed into a prime (21004913) 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, 57208 + ... + 57573.

It is an arithmetic number, because the mean of its divisors is an integer number (3558242).

Almost surely, 2^21004923 is an apocalyptic number.

21004923 is a deficient number, since it is larger than the sum of its proper divisors (7461013).

21004923 is a wasteful number, since it uses less digits than its factorization.

21004923 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114845.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21004923 is about 4583.1128068159. The cubic root of 21004923 is about 275.9139749754.

Adding to 21004923 its reverse (32940012), we get a palindrome (53944935).

The spelling of 21004923 in words is "twenty-one million, four thousand, nine hundred twenty-three".