21001045 has 8 divisors (see below), whose sum is σ = 27139896. Its totient is φ = 15508416.

The previous prime is 21001037. The next prime is 21001049. The reversal of 21001045 is 54010012.

It can be written as a sum of positive squares in 4 ways, for example, as 289444 + 20711601 = 538^2 + 4551^2 .

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 21001045 - 2³ = 21001037 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001049) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161482 + ... + 161611.

It is an arithmetic number, because the mean of its divisors is an integer number (3392487).

Almost surely, 2^21001045 is an apocalyptic number.

It is an amenable number.

21001045 is a deficient number, since it is larger than the sum of its proper divisors (6138851).

21001045 is a wasteful number, since it uses less digits than its factorization.

21001045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323111.

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21001045 is about 4582.6897123851. The cubic root of 21001045 is about 275.8969938729.

Adding to 21001045 its reverse (54010012), we get a palindrome (75011057).

The spelling of 21001045 in words is "twenty-one million, one thousand, forty-five".