21234177581 has 2 divisors, whose sum is σ = 21234177582. Its totient is φ = 21234177580.

The previous prime is 21234177571. The next prime is 21234177583. The reversal of 21234177581 is 18577143212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19235193481 + 1998984100 = 138691^2 + 44710^2 .

It is a cyclic number.

It is not a de Polignac number, because 21234177581 - 2²² = 21229983277 is a prime.

It is a super-2 number, since 2×21234177581² (a number of 21 digits) contains 22 as substring.

Together with 21234177583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21234177583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617088790 + 10617088791.

It is an arithmetic number, because the mean of its divisors is an integer number (10617088791).

Almost surely, 2^21234177581 is an apocalyptic number.

It is an amenable number.

21234177581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21234177581 is an equidigital number, since it uses as much as digits as its factorization.

21234177581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 94080, while the sum is 41.

The spelling of 21234177581 in words is "twenty-one billion, two hundred thirty-four million, one hundred seventy-seven thousand, five hundred eighty-one".