21188978502 has 8 divisors (see below), whose sum is σ = 42377957016. Its totient is φ = 7062992832.

The previous prime is 21188978501. The next prime is 21188978509. The reversal of 21188978502 is 20587988112.

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

21188978502 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21188978501) 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, 1765748203 + ... + 1765748214.

It is an arithmetic number, because the mean of its divisors is an integer number (5297244627).

Almost surely, 2^21188978502 is an apocalyptic number.

21188978502 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21188978502 is a wasteful number, since it uses less digits than its factorization.

21188978502 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3531496422.

The product of its (nonzero) digits is 645120, while the sum is 51.

The spelling of 21188978502 in words is "twenty-one billion, one hundred eighty-eight million, nine hundred seventy-eight thousand, five hundred two".