99921755661 has 64 divisors (see below), whose sum is σ = 176562892800. Its totient is φ = 48764722176.

The previous prime is 99921755651. The next prime is 99921755663. The reversal of 99921755661 is 16655712999.

It is not a de Polignac number, because 99921755661 - 2¹⁸ = 99921493517 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 99921755595 and 99921755604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99921755663) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 91360 + ... + 456278.

It is an arithmetic number, because the mean of its divisors is an integer number (2758795200).

Almost surely, 2^99921755661 is an apocalyptic number.

99921755661 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

It is an amenable number.

99921755661 is a deficient number, since it is larger than the sum of its proper divisors (76641137139).

99921755661 is a wasteful number, since it uses less digits than its factorization.

99921755661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 365018.

The product of its digits is 9185400, while the sum is 60.

It can be divided in two parts, 999217 and 55661, that added together give a triangular number (1054878 = T₁₄₅₂).

The spelling of 99921755661 in words is "ninety-nine billion, nine hundred twenty-one million, seven hundred fifty-five thousand, six hundred sixty-one".