861993551 has 16 divisors (see below), whose sum is σ = 939651840. Its totient is φ = 787438080.

The previous prime is 861993541. The next prime is 861993557. The reversal of 861993551 is 155399168.

It is a cyclic number.

It is not a de Polignac number, because 861993551 - 2²² = 857799247 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 861993496 and 861993505.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (861993557) 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 15 ways as a sum of consecutive naturals, for example, 299861 + ... + 302721.

It is an arithmetic number, because the mean of its divisors is an integer number (58728240).

Almost surely, 2^861993551 is an apocalyptic number.

861993551 is a deficient number, since it is larger than the sum of its proper divisors (77658289).

861993551 is a wasteful number, since it uses less digits than its factorization.

861993551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3394.

The product of its digits is 291600, while the sum is 47.

The square root of 861993551 is about 29359.7266846951. The cubic root of 861993551 is about 951.7027821171.

The spelling of 861993551 in words is "eight hundred sixty-one million, nine hundred ninety-three thousand, five hundred fifty-one".