61451801991 has 6 divisors (see below), whose sum is σ = 88763714000. Its totient is φ = 40967867988.

The previous prime is 61451801987. The next prime is 61451802059. The reversal of 61451801991 is 19910815416.

61451801991 is a `hidden beast` number, since 6 + 1 + 451 + 8 + 0 + 199 + 1 = 666.

It is not a de Polignac number, because 61451801991 - 2² = 61451801987 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 (61451801911) 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, 3413988991 + ... + 3413989008.

Almost surely, 2^61451801991 is an apocalyptic number.

61451801991 is a deficient number, since it is larger than the sum of its proper divisors (27311912009).

61451801991 is a wasteful number, since it uses less digits than its factorization.

61451801991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6827978005 (or 6827978002 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 45.

The spelling of 61451801991 in words is "sixty-one billion, four hundred fifty-one million, eight hundred one thousand, nine hundred ninety-one".