21521003 has 8 divisors (see below), whose sum is σ = 24963072. Its totient is φ = 18170856.

The previous prime is 21520999. The next prime is 21521009. The reversal of 21521003 is 30012512.

It is a happy number.

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 21521003 - 2² = 21520999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21521009) 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 7 ways as a sum of consecutive naturals, for example, 22475 + ... + 23412.

It is an arithmetic number, because the mean of its divisors is an integer number (3120384).

Almost surely, 2^21521003 is an apocalyptic number.

21521003 is a deficient number, since it is larger than the sum of its proper divisors (3442069).

21521003 is an equidigital number, since it uses as much as digits as its factorization.

21521003 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45961.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21521003 is about 4639.0735066390. The cubic root of 21521003 is about 278.1554045454.

Adding to 21521003 its reverse (30012512), we get a palindrome (51533515).

The spelling of 21521003 in words is "twenty-one million, five hundred twenty-one thousand, three".