21621772267061 has 2 divisors, whose sum is σ = 21621772267062. Its totient is φ = 21621772267060.

The previous prime is 21621772267049. The next prime is 21621772267129. The reversal of 21621772267061 is 16076227712612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21584665564900 + 37106702161 = 4645930^2 + 192631^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21621772267061 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21621772267661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810886133530 + 10810886133531.

It is an arithmetic number, because the mean of its divisors is an integer number (10810886133531).

Almost surely, 2^{21621772267061} is an apocalyptic number.

It is an amenable number.

21621772267061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621772267061 is an equidigital number, since it uses as much as digits as its factorization.

21621772267061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1185408, while the sum is 50.

Adding to 21621772267061 its reverse (16076227712612), we get a palindrome (37697999979673).

The spelling of 21621772267061 in words is "twenty-one trillion, six hundred twenty-one billion, seven hundred seventy-two million, two hundred sixty-seven thousand, sixty-one".