21289945 has 8 divisors (see below), whose sum is σ = 26142336. Its totient is φ = 16635696.

The previous prime is 21289913. The next prime is 21289949. The reversal of 21289945 is 54998212.

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

It is a cyclic number.

It is not a de Polignac number, because 21289945 - 2⁵ = 21289913 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21289898 and 21289907.

It is not an unprimeable number, because it can be changed into a prime (21289949) 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, 49297 + ... + 49726.

It is an arithmetic number, because the mean of its divisors is an integer number (3267792).

Almost surely, 2^21289945 is an apocalyptic number.

It is an amenable number.

21289945 is a deficient number, since it is larger than the sum of its proper divisors (4852391).

21289945 is an equidigital number, since it uses as much as digits as its factorization.

21289945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99071.

The product of its digits is 51840, while the sum is 40.

The square root of 21289945 is about 4614.1028380390. The cubic root of 21289945 is about 277.1563584387.

The spelling of 21289945 in words is "twenty-one million, two hundred eighty-nine thousand, nine hundred forty-five".