21507769696609 has 27 divisors (see below), whose sum is σ = 25438459792473. Its totient is φ = 18131344711200.

The previous prime is 21507769696607. The next prime is 21507769696631. The reversal of 21507769696609 is 90669696770512.

The square root of 21507769696609 is 4637647.

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

It can be written as a sum of positive squares in 4 ways, for example, as 9173344735009 + 12334424961600 = 3028753^2 + 3512040^2 .

It is not a de Polignac number, because 21507769696609 - 2¹ = 21507769696607 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21507769696607) 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, 1980269839 + ... + 1980280699.

It is an arithmetic number, because the mean of its divisors is an integer number (942165177499).

Almost surely, 2^{21507769696609} is an apocalyptic number.

21507769696609 is the 4637647-th square number.

21507769696609 is the 2318824-th centered octagonal number.

It is an amenable number.

21507769696609 is a deficient number, since it is larger than the sum of its proper divisors (3930690095864).

21507769696609 is an frugal number, since it uses more digits than its factorization.

21507769696609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21858 (or 10929 counting only the distinct ones).

The product of its (nonzero) digits is 462944160, while the sum is 73.

The spelling of 21507769696609 in words is "twenty-one trillion, five hundred seven billion, seven hundred sixty-nine million, six hundred ninety-six thousand, six hundred nine".