21025610091 has 12 divisors (see below), whose sum is σ = 30504118632. Its totient is φ = 13955322816.

The previous prime is 21025610087. The next prime is 21025610117. The reversal of 21025610091 is 19001652012.

21025610091 is a `hidden beast` number, since 2 + 10 + 2 + 561 + 0 + 0 + 91 = 666.

It is not a de Polignac number, because 21025610091 - 2² = 21025610087 is a prime.

It is a super-2 number, since 2×21025610091² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21025610071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5143726 + ... + 5147811.

It is an arithmetic number, because the mean of its divisors is an integer number (2542009886).

Almost surely, 2^21025610091 is an apocalyptic number.

21025610091 is a deficient number, since it is larger than the sum of its proper divisors (9478508541).

21025610091 is a wasteful number, since it uses less digits than its factorization.

21025610091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10291770 (or 10291767 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 27.

The spelling of 21025610091 in words is "twenty-one billion, twenty-five million, six hundred ten thousand, ninety-one".