21551413729 has 2 divisors, whose sum is σ = 21551413730. Its totient is φ = 21551413728.

The previous prime is 21551413669. The next prime is 21551413777. The reversal of 21551413729 is 92731415512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17470759329 + 4080654400 = 132177^2 + 63880^2 .

It is a cyclic number.

It is not a de Polignac number, because 21551413729 - 2¹⁷ = 21551282657 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21551413691 and 21551413700.

It is not a weakly prime, because it can be changed into another prime (21551410729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775706864 + 10775706865.

It is an arithmetic number, because the mean of its divisors is an integer number (10775706865).

Almost surely, 2^21551413729 is an apocalyptic number.

It is an amenable number.

21551413729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551413729 is an equidigital number, since it uses as much as digits as its factorization.

21551413729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 75600, while the sum is 40.

The spelling of 21551413729 in words is "twenty-one billion, five hundred fifty-one million, four hundred thirteen thousand, seven hundred twenty-nine".