21018789 has 18 divisors (see below), whose sum is σ = 33373158. Its totient is φ = 12738000.

The previous prime is 21018779. The next prime is 21018799. The reversal of 21018789 is 98781012.

It is an interprime number because it is at equal distance from previous prime (21018779) and next prime (21018799).

It can be written as a sum of positive squares in only one way, i.e., 18404100 + 2614689 = 4290^2 + 1617^2 .

It is not a de Polignac number, because 21018789 - 2²⁰ = 19970213 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018719) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 8562 + ... + 10739.

Almost surely, 2^21018789 is an apocalyptic number.

It is an amenable number.

21018789 is a deficient number, since it is larger than the sum of its proper divisors (12354369).

21018789 is a wasteful number, since it uses less digits than its factorization.

21018789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19329 (or 19315 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 21018789 is about 4584.6252845789. The cubic root of 21018789 is about 275.9746747399.

It can be divided in two parts, 210187 and 89, that added together give a triangular number (210276 = T₆₄₈).

The spelling of 21018789 in words is "twenty-one million, eighteen thousand, seven hundred eighty-nine".