21207571 has 8 divisors (see below), whose sum is σ = 26440704. Its totient is φ = 16525320.

The previous prime is 21207569. The next prime is 21207581. The reversal of 21207571 is 17570212.

It is a happy number.

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

It is not a de Polignac number, because 21207571 - 2¹ = 21207569 is a prime.

It is a super-2 number, since 2×21207571² = 899522135440082, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21207581) 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, 137635 + ... + 137788.

It is an arithmetic number, because the mean of its divisors is an integer number (3305088).

Almost surely, 2^21207571 is an apocalyptic number.

21207571 is a deficient number, since it is larger than the sum of its proper divisors (5233133).

21207571 is a wasteful number, since it uses less digits than its factorization.

21207571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275441.

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 21207571 is about 4605.1678579613. The cubic root of 21207571 is about 276.7984432166.

Adding to 21207571 its reverse (17570212), we get a palindrome (38777783).

It can be divided in two parts, 2 and 1207571, that multiplied together give a palindrome (2415142).

The spelling of 21207571 in words is "twenty-one million, two hundred seven thousand, five hundred seventy-one".