21129381216 has 36 divisors (see below), whose sum is σ = 60086678652. Its totient is φ = 7043126976.

The previous prime is 21129381191. The next prime is 21129381257. The reversal of 21129381216 is 61218392112.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36682666 + ... + 36683241.

It is an arithmetic number, because the mean of its divisors is an integer number (1669074407).

Almost surely, 2^21129381216 is an apocalyptic number.

It is an amenable number.

21129381216 is an abundant number, since it is smaller than the sum of its proper divisors (38957297436).

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

21129381216 is a wasteful number, since it uses less digits than its factorization.

21129381216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73365923 (or 73365912 counting only the distinct ones).

The product of its digits is 10368, while the sum is 36.

The spelling of 21129381216 in words is "twenty-one billion, one hundred twenty-nine million, three hundred eighty-one thousand, two hundred sixteen".