21002459 has 4 divisors (see below), whose sum is σ = 21020160. Its totient is φ = 20984760.

The previous prime is 21002431. The next prime is 21002461. The reversal of 21002459 is 95420012.

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 21002459 - 2⁸ = 21002203 is a prime.

It is a super-2 number, since 2×21002459² = 882206568093362, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002479) 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, 6932 + ... + 9489.

It is an arithmetic number, because the mean of its divisors is an integer number (5255040).

Almost surely, 2^21002459 is an apocalyptic number.

21002459 is a deficient number, since it is larger than the sum of its proper divisors (17701).

21002459 is a wasteful number, since it uses less digits than its factorization.

21002459 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17700.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21002459 is about 4582.8439859982. The cubic root of 21002459 is about 275.9031857806.

The spelling of 21002459 in words is "twenty-one million, two thousand, four hundred fifty-nine".