21621402154321 has 2 divisors, whose sum is σ = 21621402154322. Its totient is φ = 21621402154320.

The previous prime is 21621402154309. The next prime is 21621402154349. The reversal of 21621402154321 is 12345120412612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21594274417296 + 27127737025 = 4646964^2 + 164705^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21621402154321 is a prime.

It is a super-2 number, since 2×21621402154321² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21621402154381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810701077160 + 10810701077161.

It is an arithmetic number, because the mean of its divisors is an integer number (10810701077161).

Almost surely, 2^{21621402154321} is an apocalyptic number.

It is an amenable number.

21621402154321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621402154321 is an equidigital number, since it uses as much as digits as its factorization.

21621402154321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23040, while the sum is 34.

Adding to 21621402154321 its reverse (12345120412612), we get a palindrome (33966522566933).

The spelling of 21621402154321 in words is "twenty-one trillion, six hundred twenty-one billion, four hundred two million, one hundred fifty-four thousand, three hundred twenty-one".