21405445 has 16 divisors (see below), whose sum is σ = 26588160. Its totient is φ = 16533504.

The previous prime is 21405427. The next prime is 21405467. The reversal of 21405445 is 54450412.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21405445 - 2¹³ = 21397253 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17989 + ... + 19141.

It is an arithmetic number, because the mean of its divisors is an integer number (1661760).

Almost surely, 2^21405445 is an apocalyptic number.

It is an amenable number.

21405445 is a deficient number, since it is larger than the sum of its proper divisors (5182715).

21405445 is a wasteful number, since it uses less digits than its factorization.

21405445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1284.

The product of its (nonzero) digits is 3200, while the sum is 25.

The square root of 21405445 is about 4626.6018847530. The cubic root of 21405445 is about 277.6566547780.

Adding to 21405445 its reverse (54450412), we get a palindrome (75855857).

The spelling of 21405445 in words is "twenty-one million, four hundred five thousand, four hundred forty-five".