21249875691 has 96 divisors (see below), whose sum is σ = 36363294720. Its totient is φ = 12150432000.

The previous prime is 21249875659. The next prime is 21249875701. The reversal of 21249875691 is 19657894212.

It is a happy number.

21249875691 is a `hidden beast` number, since 2 + 12 + 498 + 7 + 56 + 91 = 666.

It is not a de Polignac number, because 21249875691 - 2⁵ = 21249875659 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21249875891) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 15476281 + ... + 15477653.

It is an arithmetic number, because the mean of its divisors is an integer number (378784320).

Almost surely, 2^21249875691 is an apocalyptic number.

21249875691 is a deficient number, since it is larger than the sum of its proper divisors (15113419029).

21249875691 is a wasteful number, since it uses less digits than its factorization.

21249875691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1506 (or 1459 counting only the distinct ones).

The product of its digits is 2177280, while the sum is 54.

The spelling of 21249875691 in words is "twenty-one billion, two hundred forty-nine million, eight hundred seventy-five thousand, six hundred ninety-one".