21815871478 has 16 divisors (see below), whose sum is σ = 34461443520. Its totient is φ = 10329234696.

The previous prime is 21815871449. The next prime is 21815871491. The reversal of 21815871478 is 87417851812.

It is a happy number.

It is a super-2 number, since 2×21815871478² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40476 + ... + 212767.

It is an arithmetic number, because the mean of its divisors is an integer number (2153840220).

Almost surely, 2^21815871478 is an apocalyptic number.

21815871478 is a deficient number, since it is larger than the sum of its proper divisors (12645572042).

21815871478 is a wasteful number, since it uses less digits than its factorization.

21815871478 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 255531.

The product of its digits is 1003520, while the sum is 52.

The spelling of 21815871478 in words is "twenty-one billion, eight hundred fifteen million, eight hundred seventy-one thousand, four hundred seventy-eight".