21278003 has 4 divisors (see below), whose sum is σ = 21289008. Its totient is φ = 21267000.

The previous prime is 21277987. The next prime is 21278021. The reversal of 21278003 is 30087212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21278003 - 2⁴ = 21277987 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 21278003.

It is not an unprimeable number, because it can be changed into a prime (21278063) 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, 1748 + ... + 6753.

It is an arithmetic number, because the mean of its divisors is an integer number (5322252).

Almost surely, 2^21278003 is an apocalyptic number.

21278003 is a deficient number, since it is larger than the sum of its proper divisors (11005).

21278003 is an equidigital number, since it uses as much as digits as its factorization.

21278003 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11004.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21278003 is about 4612.8085804638. The cubic root of 21278003 is about 277.1045277071.

Adding to 21278003 its sum of digits (23), we get a triangular number (21278026 = T₆₅₂₃).

The spelling of 21278003 in words is "twenty-one million, two hundred seventy-eight thousand, three".