21717673261 has 2 divisors, whose sum is σ = 21717673262. Its totient is φ = 21717673260.

The previous prime is 21717673231. The next prime is 21717673279. The reversal of 21717673261 is 16237671712.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10905624900 + 10812048361 = 104430^2 + 103981^2 .

It is a cyclic number.

It is not a de Polignac number, because 21717673261 - 2²⁷ = 21583455533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21717673231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10858836630 + 10858836631.

It is an arithmetic number, because the mean of its divisors is an integer number (10858836631).

Almost surely, 2^21717673261 is an apocalyptic number.

It is an amenable number.

21717673261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21717673261 is an equidigital number, since it uses as much as digits as its factorization.

21717673261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 148176, while the sum is 43.

The spelling of 21717673261 in words is "twenty-one billion, seven hundred seventeen million, six hundred seventy-three thousand, two hundred sixty-one".