21011221550 has 24 divisors (see below), whose sum is σ = 42633679752. Its totient is φ = 7640444000.

The previous prime is 21011221531. The next prime is 21011221577. The reversal of 21011221550 is 5512211012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19100561 + ... + 19101660.

It is an arithmetic number, because the mean of its divisors is an integer number (1776403323).

Almost surely, 2^21011221550 is an apocalyptic number.

21011221550 is an abundant number, since it is smaller than the sum of its proper divisors (21622458202).

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

21011221550 is a wasteful number, since it uses less digits than its factorization.

21011221550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38202244 (or 38202239 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 20.

Adding to 21011221550 its reverse (5512211012), we get a palindrome (26523432562).

The spelling of 21011221550 in words is "twenty-one billion, eleven million, two hundred twenty-one thousand, five hundred fifty".