21551473 has 8 divisors (see below), whose sum is σ = 21853800. Its totient is φ = 21251328.

The previous prime is 21551459. The next prime is 21551503. The reversal of 21551473 is 37415512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 3301489 + 18249984 = 1817^2 + 4272^2 .

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 21551473 - 2⁵ = 21551441 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21551423) 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, 30043 + ... + 30751.

It is an arithmetic number, because the mean of its divisors is an integer number (2731725).

Almost surely, 2^21551473 is an apocalyptic number.

It is an amenable number.

21551473 is a deficient number, since it is larger than the sum of its proper divisors (302327).

21551473 is a wasteful number, since it uses less digits than its factorization.

21551473 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1091.

The product of its digits is 4200, while the sum is 28.

The square root of 21551473 is about 4642.3564059645. The cubic root of 21551473 is about 278.2866158777.

Adding to 21551473 its reverse (37415512), we get a palindrome (58966985).

The spelling of 21551473 in words is "twenty-one million, five hundred fifty-one thousand, four hundred seventy-three".