21621271263541 has 2 divisors, whose sum is σ = 21621271263542. Its totient is φ = 21621271263540.

The previous prime is 21621271263511. The next prime is 21621271263587. The reversal of 21621271263541 is 14536217212612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18542109663025 + 3079161600516 = 4306055^2 + 1754754^2 .

It is a cyclic number.

It is not a de Polignac number, because 21621271263541 - 2²¹ = 21621269166389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21621271263511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810635631770 + 10810635631771.

It is an arithmetic number, because the mean of its divisors is an integer number (10810635631771).

Almost surely, 2^{21621271263541} is an apocalyptic number.

It is an amenable number.

21621271263541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621271263541 is an equidigital number, since it uses as much as digits as its factorization.

21621271263541 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 241920, while the sum is 43.

The spelling of 21621271263541 in words is "twenty-one trillion, six hundred twenty-one billion, two hundred seventy-one million, two hundred sixty-three thousand, five hundred forty-one".