21211789 has 8 divisors (see below), whose sum is σ = 22095000. Its totient is φ = 20338752.

The previous prime is 21211783. The next prime is 21211807. The reversal of 21211789 is 98711212.

It can be written as a sum of positive squares in 4 ways, for example, as 5546025 + 15665764 = 2355^2 + 3958^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21211789 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21211789.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211783) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1867 + ... + 6775.

It is an arithmetic number, because the mean of its divisors is an integer number (2761875).

Almost surely, 2^21211789 is an apocalyptic number.

21211789 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21211789 is a deficient number, since it is larger than the sum of its proper divisors (883211).

21211789 is a wasteful number, since it uses less digits than its factorization.

21211789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5087.

The product of its digits is 2016, while the sum is 31.

The square root of 21211789 is about 4605.6257989550. The cubic root of 21211789 is about 276.8167929282.

The spelling of 21211789 in words is "twenty-one million, two hundred eleven thousand, seven hundred eighty-nine".