91845665821 has 32 divisors (see below), whose sum is σ = 114495171840. Its totient is φ = 71735583744.

The previous prime is 91845665819. The next prime is 91845665827. The reversal of 91845665821 is 12856654819.

It is a cyclic number.

It is not a de Polignac number, because 91845665821 - 2¹ = 91845665819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91845665827) 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, 10970325 + ... + 10978693.

It is an arithmetic number, because the mean of its divisors is an integer number (3577974120).

Almost surely, 2^91845665821 is an apocalyptic number.

91845665821 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

It is an amenable number.

91845665821 is a deficient number, since it is larger than the sum of its proper divisors (22649506019).

91845665821 is a wasteful number, since it uses less digits than its factorization.

91845665821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9925.

The product of its digits is 4147200, while the sum is 55.

The spelling of 91845665821 in words is "ninety-one billion, eight hundred forty-five million, six hundred sixty-five thousand, eight hundred twenty-one".