21390045 has 8 divisors (see below), whose sum is σ = 34224096. Its totient is φ = 11408016.

The previous prime is 21390043. The next prime is 21390071. The reversal of 21390045 is 54009312.

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

It is not a de Polignac number, because 21390045 - 2¹ = 21390043 is a prime.

It is a super-3 number, since 3×21390045³ (a number of 23 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21389997 and 21390024.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390041) 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, 712987 + ... + 713016.

It is an arithmetic number, because the mean of its divisors is an integer number (4278012).

Almost surely, 2^21390045 is an apocalyptic number.

It is an amenable number.

21390045 is a deficient number, since it is larger than the sum of its proper divisors (12834051).

21390045 is a wasteful number, since it uses less digits than its factorization.

21390045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1426011.

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 21390045 is about 4624.9372968723. The cubic root of 21390045 is about 277.5900527473.

Adding to 21390045 its reverse (54009312), we get a palindrome (75399357).

The spelling of 21390045 in words is "twenty-one million, three hundred ninety thousand, forty-five".