21571849 has 4 divisors (see below), whose sum is σ = 23231236. Its totient is φ = 19912464.

The previous prime is 21571841. The next prime is 21571867. The reversal of 21571849 is 94817512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2805625 + 18766224 = 1675^2 + 4332^2 .

It is not a de Polignac number, because 21571849 - 2³ = 21571841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21571841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 829674 + ... + 829699.

It is an arithmetic number, because the mean of its divisors is an integer number (5807809).

Almost surely, 2^21571849 is an apocalyptic number.

It is an amenable number.

21571849 is a deficient number, since it is larger than the sum of its proper divisors (1659387).

21571849 is a wasteful number, since it uses less digits than its factorization.

21571849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1659386.

The product of its digits is 20160, while the sum is 37.

The square root of 21571849 is about 4644.5504626390. The cubic root of 21571849 is about 278.3742909675.

The spelling of 21571849 in words is "twenty-one million, five hundred seventy-one thousand, eight hundred forty-nine".