21528379691 has 32 divisors (see below), whose sum is σ = 27456135168. Its totient is φ = 16420734720.

The previous prime is 21528379681. The next prime is 21528379693. The reversal of 21528379691 is 19697382512.

It is not a de Polignac number, because 21528379691 - 2⁶ = 21528379627 is a prime.

It is a super-3 number, since 3×21528379691³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21528379693) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 727415 + ... + 756431.

It is an arithmetic number, because the mean of its divisors is an integer number (858004224).

Almost surely, 2^21528379691 is an apocalyptic number.

21528379691 is a deficient number, since it is larger than the sum of its proper divisors (5927755477).

21528379691 is a wasteful number, since it uses less digits than its factorization.

21528379691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29331.

The product of its digits is 1632960, while the sum is 53.

The spelling of 21528379691 in words is "twenty-one billion, five hundred twenty-eight million, three hundred seventy-nine thousand, six hundred ninety-one".