21040121609 has 12 divisors (see below), whose sum is σ = 22793546700. Its totient is φ = 19412737344.

The previous prime is 21040121593. The next prime is 21040121633. The reversal of 21040121609 is 90612104012.

It can be written as a sum of positive squares in 6 ways, for example, as 13139578384 + 7900543225 = 114628^2 + 88885^2 .

It is not a de Polignac number, because 21040121609 - 2⁴ = 21040121593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21040121699) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 356027 + ... + 410895.

It is an arithmetic number, because the mean of its divisors is an integer number (1899462225).

Almost surely, 2^21040121609 is an apocalyptic number.

It is an amenable number.

21040121609 is a deficient number, since it is larger than the sum of its proper divisors (1753425091).

21040121609 is a wasteful number, since it uses less digits than its factorization.

21040121609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57164 (or 57151 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 26.

The spelling of 21040121609 in words is "twenty-one billion, forty million, one hundred twenty-one thousand, six hundred nine".