21420445 has 8 divisors (see below), whose sum is σ = 25847640. Its totient is φ = 17040960.

The previous prime is 21420439. The next prime is 21420449. The reversal of 21420445 is 54402412.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 205209 + 21215236 = 453^2 + 4606^2 .

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

It is not a de Polignac number, because 21420445 - 2⁹ = 21419933 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420449) 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, 10930 + ... + 12739.

It is an arithmetic number, because the mean of its divisors is an integer number (3230955).

Almost surely, 2^21420445 is an apocalyptic number.

It is an amenable number.

21420445 is a deficient number, since it is larger than the sum of its proper divisors (4427195).

21420445 is a wasteful number, since it uses less digits than its factorization.

21420445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23855.

The product of its (nonzero) digits is 1280, while the sum is 22.

The square root of 21420445 is about 4628.2226610223. Note that the first 3 decimals coincide. The cubic root of 21420445 is about 277.7214961825.

Adding to 21420445 its reverse (54402412), we get a palindrome (75822857).

The spelling of 21420445 in words is "twenty-one million, four hundred twenty thousand, four hundred forty-five".