21998345 has 8 divisors (see below), whose sum is σ = 27042120. Its totient is φ = 17169280.

The previous prime is 21998341. The next prime is 21998359. The reversal of 21998345 is 54389912.

21998345 = 3316² + 3317².

It can be written as a sum of positive squares in 4 ways, for example, as 440896 + 21557449 = 664^2 + 4643^2 .

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

It is not a de Polignac number, because 21998345 - 2² = 21998341 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is not an unprimeable number, because it can be changed into a prime (21998341) 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 7 ways as a sum of consecutive naturals, for example, 53450 + ... + 53859.

It is an arithmetic number, because the mean of its divisors is an integer number (3380265).

Almost surely, 2^21998345 is an apocalyptic number.

21998345 is the 3317-th centered square number.

It is an amenable number.

21998345 is a deficient number, since it is larger than the sum of its proper divisors (5043775).

21998345 is a wasteful number, since it uses less digits than its factorization.

21998345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107355.

The product of its digits is 77760, while the sum is 41.

The square root of 21998345 is about 4690.2393329126. The cubic root of 21998345 is about 280.1969065634.

The spelling of 21998345 in words is "twenty-one million, nine hundred ninety-eight thousand, three hundred forty-five".