21530173651 has 24 divisors (see below), whose sum is σ = 26530981056. Its totient is φ = 17360743680.

The previous prime is 21530173633. The next prime is 21530173673. The reversal of 21530173651 is 15637103512.

It is not a de Polignac number, because 21530173651 - 2⁹ = 21530173139 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21530173601) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2300241 + ... + 2309581.

It is an arithmetic number, because the mean of its divisors is an integer number (1105457544).

Almost surely, 2^21530173651 is an apocalyptic number.

21530173651 is a deficient number, since it is larger than the sum of its proper divisors (5000807405).

21530173651 is a wasteful number, since it uses less digits than its factorization.

21530173651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12139 (or 12132 counting only the distinct ones).

The product of its (nonzero) digits is 18900, while the sum is 34.

The spelling of 21530173651 in words is "twenty-one billion, five hundred thirty million, one hundred seventy-three thousand, six hundred fifty-one".