21018629 has 4 divisors (see below), whose sum is σ = 21045420. Its totient is φ = 20991840.

The previous prime is 21018623. The next prime is 21018631. The reversal of 21018629 is 92681012.

21018629 is nontrivially palindromic in base 4.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15249025 + 5769604 = 3905^2 + 2402^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21018629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018623) 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, 12182 + ... + 13799.

It is an arithmetic number, because the mean of its divisors is an integer number (5261355).

Almost surely, 2^21018629 is an apocalyptic number.

It is an amenable number.

21018629 is a deficient number, since it is larger than the sum of its proper divisors (26791).

21018629 is an equidigital number, since it uses as much as digits as its factorization.

21018629 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26790.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21018629 is about 4584.6078349189. The cubic root of 21018629 is about 275.9739744766.

The spelling of 21018629 in words is "twenty-one million, eighteen thousand, six hundred twenty-nine".