21011121072 has 30 divisors (see below), whose sum is σ = 58801957292. Its totient is φ = 7003706976.

The previous prime is 21011121059. The next prime is 21011121073. The reversal of 21011121072 is 27012111012.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21011121073) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 72955138 + ... + 72955425.

Almost surely, 2^21011121072 is an apocalyptic number.

It is an amenable number.

21011121072 is an abundant number, since it is smaller than the sum of its proper divisors (37790836220).

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

21011121072 is a wasteful number, since it uses less digits than its factorization.

21011121072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145910577 (or 145910568 counting only the distinct ones).

The product of its (nonzero) digits is 56, while the sum is 18.

Adding to 21011121072 its reverse (27012111012), we get a palindrome (48023232084).

The spelling of 21011121072 in words is "twenty-one billion, eleven million, one hundred twenty-one thousand, seventy-two".