21278829578 has 4 divisors (see below), whose sum is σ = 31918244370. Its totient is φ = 10639414788.

The previous prime is 21278829577. The next prime is 21278829601. The reversal of 21278829578 is 87592887212.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 18736955689 + 2541873889 = 136883^2 + 50417^2 .

It is not an unprimeable number, because it can be changed into a prime (21278829577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5319707393 + ... + 5319707396.

Almost surely, 2^21278829578 is an apocalyptic number.

21278829578 is a deficient number, since it is larger than the sum of its proper divisors (10639414792).

21278829578 is a wasteful number, since it uses less digits than its factorization.

21278829578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10639414791.

The product of its digits is 9031680, while the sum is 59.

The spelling of 21278829578 in words is "twenty-one billion, two hundred seventy-eight million, eight hundred twenty-nine thousand, five hundred seventy-eight".