21531320775 has 30 divisors (see below), whose sum is σ = 39883452752. Its totient is φ = 11483370000.

The previous prime is 21531320689. The next prime is 21531320791. The reversal of 21531320775 is 57702313512.

It is a happy number.

21531320775 is a `hidden beast` number, since 21 + 531 + 32 + 0 + 7 + 75 = 666.

It is not a de Polignac number, because 21531320775 - 2⁷ = 21531320647 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 5314351 + ... + 5318400.

Almost surely, 2^21531320775 is an apocalyptic number.

21531320775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21531320775 is a deficient number, since it is larger than the sum of its proper divisors (18352131977).

21531320775 is a wasteful number, since it uses less digits than its factorization.

21531320775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10632773 (or 10632759 counting only the distinct ones).

The product of its (nonzero) digits is 44100, while the sum is 36.

The spelling of 21531320775 in words is "twenty-one billion, five hundred thirty-one million, three hundred twenty thousand, seven hundred seventy-five".