21801389 has 4 divisors (see below), whose sum is σ = 21871356. Its totient is φ = 21731424.

The previous prime is 21801383. The next prime is 21801407. The reversal of 21801389 is 98310812.

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 9954025 + 11847364 = 3155^2 + 3442^2 .

It is a cyclic number.

It is not a de Polignac number, because 21801389 - 2⁸ = 21801133 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 (21801383) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34514 + ... + 35139.

It is an arithmetic number, because the mean of its divisors is an integer number (5467839).

Almost surely, 2^21801389 is an apocalyptic number.

It is an amenable number.

21801389 is a deficient number, since it is larger than the sum of its proper divisors (69967).

21801389 is an equidigital number, since it uses as much as digits as its factorization.

21801389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69966.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 21801389 is about 4669.1957551596. The cubic root of 21801389 is about 279.3581770304.

The spelling of 21801389 in words is "twenty-one million, eight hundred one thousand, three hundred eighty-nine".