21358945609 has 9 divisors (see below), whose sum is σ = 21587432871. Its totient is φ = 21132856200.

The previous prime is 21358945591. The next prime is 21358945633. The reversal of 21358945609 is 90654985312.

The square root of 21358945609 is 146147.

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

It can be written as a sum of positive squares in only one way, i.e., 20521422009 + 837523600 = 143253^2 + 28940^2 .

It is not a de Polignac number, because 21358945609 - 2⁵ = 21358945577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21358945669) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 14760124 + ... + 14761570.

Almost surely, 2^21358945609 is an apocalyptic number.

21358945609 is the 146147-th square number.

21358945609 is the 73074-th centered octagonal number.

It is an amenable number.

21358945609 is a deficient number, since it is larger than the sum of its proper divisors (228487262).

21358945609 is an frugal number, since it uses more digits than its factorization.

21358945609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3096 (or 1548 counting only the distinct ones).

The product of its (nonzero) digits is 2332800, while the sum is 52.

The spelling of 21358945609 in words is "twenty-one billion, three hundred fifty-eight million, nine hundred forty-five thousand, six hundred nine".