21655044165421 has 2 divisors, whose sum is σ = 21655044165422. Its totient is φ = 21655044165420.

The previous prime is 21655044165413. The next prime is 21655044165431. The reversal of 21655044165421 is 12456144055612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21308286888100 + 346757277321 = 4616090^2 + 588861^2 .

It is a cyclic number.

It is not a de Polignac number, because 21655044165421 - 2³ = 21655044165413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21655044165431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827522082710 + 10827522082711.

It is an arithmetic number, because the mean of its divisors is an integer number (10827522082711).

Almost surely, 2^{21655044165421} is an apocalyptic number.

It is an amenable number.

21655044165421 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655044165421 is an equidigital number, since it uses as much as digits as its factorization.

21655044165421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152000, while the sum is 46.

The spelling of 21655044165421 in words is "twenty-one trillion, six hundred fifty-five billion, forty-four million, one hundred sixty-five thousand, four hundred twenty-one".