61199991 has 6 divisors (see below), whose sum is σ = 88400000. Its totient is φ = 40799988.

The previous prime is 61199981. The next prime is 61199993. The reversal of 61199991 is 19999116.

It is not a de Polignac number, because 61199991 - 2⁵ = 61199959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61199993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3399991 + ... + 3400008.

Almost surely, 2^61199991 is an apocalyptic number.

61199991 is a deficient number, since it is larger than the sum of its proper divisors (27200009).

61199991 is a wasteful number, since it uses less digits than its factorization.

61199991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6800005 (or 6800002 counting only the distinct ones).

The product of its digits is 39366, while the sum is 45.

The square root of 61199991 is about 7823.0423110194. The cubic root of 61199991 is about 394.0794479346.

It can be divided in two parts, 6119 and 9991, that added together give a triangular number (16110 = T₁₇₉).

The spelling of 61199991 in words is "sixty-one million, one hundred ninety-nine thousand, nine hundred ninety-one".