21155055078 has 16 divisors (see below), whose sum is σ = 42311566080. Its totient is φ = 7051442376.

The previous prime is 21155055013. The next prime is 21155055079. The reversal of 21155055078 is 87055055112.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155055079) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 252943 + ... + 326021.

It is an arithmetic number, because the mean of its divisors is an integer number (2644472880).

Almost surely, 2^21155055078 is an apocalyptic number.

21155055078 is an abundant number, since it is smaller than the sum of its proper divisors (21156511002).

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

21155055078 is a wasteful number, since it uses less digits than its factorization.

21155055078 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121331.

The product of its (nonzero) digits is 70000, while the sum is 39.

The spelling of 21155055078 in words is "twenty-one billion, one hundred fifty-five million, fifty-five thousand, seventy-eight".