21011051221 has 16 divisors (see below), whose sum is σ = 21563642880. Its totient is φ = 20463125760.

The previous prime is 21011051209. The next prime is 21011051227. The reversal of 21011051221 is 12215011012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21011051221 is a prime.

It is a super-2 number, since 2×21011051221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21011051195 and 21011051204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011051227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11228916 + ... + 11230786.

It is an arithmetic number, because the mean of its divisors is an integer number (1347727680).

Almost surely, 2^21011051221 is an apocalyptic number.

It is an amenable number.

21011051221 is a deficient number, since it is larger than the sum of its proper divisors (552591659).

21011051221 is a wasteful number, since it uses less digits than its factorization.

21011051221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2964.

The product of its (nonzero) digits is 40, while the sum is 16.

Adding to 21011051221 its reverse (12215011012), we get a palindrome (33226062233).

The spelling of 21011051221 in words is "twenty-one billion, eleven million, fifty-one thousand, two hundred twenty-one".