61857991 has 8 divisors (see below), whose sum is σ = 67420080. Its totient is φ = 56410752.

The previous prime is 61857979. The next prime is 61857997. The reversal of 61857991 is 19975816.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61857991 is a prime.

It is a super-2 number, since 2×61857991² = 7652822101112162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61857997) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27586 + ... + 29743.

It is an arithmetic number, because the mean of its divisors is an integer number (8427510).

Almost surely, 2^61857991 is an apocalyptic number.

61857991 is a deficient number, since it is larger than the sum of its proper divisors (5562089).

61857991 is a wasteful number, since it uses less digits than its factorization.

61857991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57425.

The product of its digits is 136080, while the sum is 46.

The square root of 61857991 is about 7864.9851239529. The cubic root of 61857991 is about 395.4867491936.

The spelling of 61857991 in words is "sixty-one million, eight hundred fifty-seven thousand, nine hundred ninety-one".