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99999991 = 7137691429
BaseRepresentation
bin1011111010111…
…10000011110111
320222011112012101
411331132003313
5201044444431
613531202531
72322662110
oct575360367
9228145171
1099999991
11514a1523
12295a6447
13179437c0
14d3d1207
158ba4961
hex5f5e0f7

99999991 has 16 divisors (see below), whose sum is σ = 123323200. Its totient is φ = 78962688.

The previous prime is 99999989. The next prime is 100000007. The reversal of 99999991 is 19999999.

It is not a de Polignac number, because 99999991 - 21 = 99999989 is a prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99999931) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 69265 + ... + 70693.

It is an arithmetic number, because the mean of its divisors is an integer number (7707700).

Almost surely, 299999991 is an apocalyptic number.

99999991 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

99999991 is a deficient number, since it is larger than the sum of its proper divisors (23323209).

99999991 is a wasteful number, since it uses less digits than its factorization.

99999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2218.

The product of its digits is 4782969, while the sum is 64.

The square root of 99999991 is about 9999.9995500000. Note that the first 3 decimals coincide. The cubic root of 99999991 is about 464.1588694365.

It can be divided in two parts, 9999999 and 1, that added together give a 7-th power (10000000 = 107).

The spelling of 99999991 in words is "ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety-one".

Divisors: 1 7 13 91 769 1429 5383 9997 10003 18577 69979 130039 1098901 7692307 14285713 99999991