21871513 has 4 divisors (see below), whose sum is σ = 22010980. Its totient is φ = 21732048.

The previous prime is 21871453. The next prime is 21871519. The reversal of 21871513 is 31517812.

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 12581209 + 9290304 = 3547^2 + 3048^2 .

It is a cyclic number.

It is not a de Polignac number, because 21871513 - 2²¹ = 19774361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21871519) 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, 69498 + ... + 69811.

It is an arithmetic number, because the mean of its divisors is an integer number (5502745).

Almost surely, 2^21871513 is an apocalyptic number.

It is an amenable number.

21871513 is a deficient number, since it is larger than the sum of its proper divisors (139467).

21871513 is a wasteful number, since it uses less digits than its factorization.

21871513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139466.

The product of its digits is 1680, while the sum is 28.

The square root of 21871513 is about 4676.6989426304. The cubic root of 21871513 is about 279.6573742798.

The spelling of 21871513 in words is "twenty-one million, eight hundred seventy-one thousand, five hundred thirteen".