61615991 has 4 divisors (see below), whose sum is σ = 61738992. Its totient is φ = 61492992.

The previous prime is 61615987. The next prime is 61615999. The reversal of 61615991 is 19951616.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 61615991 - 2² = 61615987 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 (61615999) 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 3 ways as a sum of consecutive naturals, for example, 60746 + ... + 61751.

It is an arithmetic number, because the mean of its divisors is an integer number (15434748).

Almost surely, 2^61615991 is an apocalyptic number.

61615991 is a deficient number, since it is larger than the sum of its proper divisors (123001).

61615991 is a wasteful number, since it uses less digits than its factorization.

61615991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123000.

The product of its digits is 14580, while the sum is 38.

The square root of 61615991 is about 7849.5854030643. The cubic root of 61615991 is about 394.9703358592.

The spelling of 61615991 in words is "sixty-one million, six hundred fifteen thousand, nine hundred ninety-one".