21621211445161 has 4 divisors (see below), whose sum is σ = 21819571183300. Its totient is φ = 21422851707024.

The previous prime is 21621211445159. The next prime is 21621211445233. The reversal of 21621211445161 is 16154411212612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13546492469136 + 8074718976025 = 3680556^2 + 2841605^2 .

It is a cyclic number.

It is not a de Polignac number, because 21621211445161 - 2¹ = 21621211445159 is a prime.

It is a super-2 number, since 2×21621211445161² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21621211445161.

It is not an unprimeable number, because it can be changed into a prime (21621211446161) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99179868906 + ... + 99179869123.

It is an arithmetic number, because the mean of its divisors is an integer number (5454892795825).

Almost surely, 2^{21621211445161} is an apocalyptic number.

It is an amenable number.

21621211445161 is a deficient number, since it is larger than the sum of its proper divisors (198359738139).

21621211445161 is a wasteful number, since it uses less digits than its factorization.

21621211445161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198359738138.

The product of its digits is 23040, while the sum is 37.

Adding to 21621211445161 its reverse (16154411212612), we get a palindrome (37775622657773).

The spelling of 21621211445161 in words is "twenty-one trillion, six hundred twenty-one billion, two hundred eleven million, four hundred forty-five thousand, one hundred sixty-one".