21000789 has 12 divisors (see below), whose sum is σ = 31458336. Its totient is φ = 14000364.

The previous prime is 21000779. The next prime is 21000803. The reversal of 21000789 is 98700012.

It is not a de Polignac number, because 21000789 - 2⁸ = 21000533 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000709) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 42969 + ... + 43454.

It is an arithmetic number, because the mean of its divisors is an integer number (2621528).

Almost surely, 2^21000789 is an apocalyptic number.

It is an amenable number.

21000789 is a deficient number, since it is larger than the sum of its proper divisors (10457547).

21000789 is an frugal number, since it uses more digits than its factorization.

21000789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86438 (or 86426 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 21000789 is about 4582.6617811050. The cubic root of 21000789 is about 275.8958728189.

The spelling of 21000789 in words is "twenty-one million, seven hundred eighty-nine", and thus it is an aban number.