21529108162809 has 27 divisors (see below), whose sum is σ = 33674016319437. Its totient is φ = 13248570587616.

The previous prime is 21529108162801. The next prime is 21529108162823. The reversal of 21529108162809 is 90826180192512.

The square root of 21529108162809 is 4639947.

It is a perfect power (a square), and thus also a powerful number.

21529108162809 is a `hidden beast` number, since 2 + 1 + 5 + 2 + 9 + 1 + 0 + 8 + 1 + 628 + 0 + 9 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 9293943668409 + 12235164494400 = 3048597^2 + 3497880^2 .

It is not a de Polignac number, because 21529108162809 - 2³ = 21529108162801 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21529108162801) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 180898447 + ... + 181017419.

Almost surely, 2^{21529108162809} is an apocalyptic number.

21529108162809 is the 4639947-th square number.

21529108162809 is the 2319974-th centered octagonal number.

It is an amenable number.

21529108162809 is a deficient number, since it is larger than the sum of its proper divisors (12144908156628).

21529108162809 is an frugal number, since it uses more digits than its factorization.

21529108162809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 237978 (or 118989 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 54.

The spelling of 21529108162809 in words is "twenty-one trillion, five hundred twenty-nine billion, one hundred eight million, one hundred sixty-two thousand, eight hundred nine".