21512789 has 2 divisors, whose sum is σ = 21512790. Its totient is φ = 21512788.

The previous prime is 21512783. The next prime is 21512801. The reversal of 21512789 is 98721512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11336689 + 10176100 = 3367^2 + 3190^2 .

It is a cyclic number.

It is not a de Polignac number, because 21512789 - 2¹⁶ = 21447253 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21512783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756394 + 10756395.

It is an arithmetic number, because the mean of its divisors is an integer number (10756395).

Almost surely, 2^21512789 is an apocalyptic number.

It is an amenable number.

21512789 is a deficient number, since it is larger than the sum of its proper divisors (1).

21512789 is an equidigital number, since it uses as much as digits as its factorization.

21512789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10080, while the sum is 35.

The square root of 21512789 is about 4638.1881160643. The cubic root of 21512789 is about 278.1200118451.

The spelling of 21512789 in words is "twenty-one million, five hundred twelve thousand, seven hundred eighty-nine".