61999978 has 4 divisors (see below), whose sum is σ = 92999970. Its totient is φ = 30999988.

The previous prime is 61999967. The next prime is 61999997. The reversal of 61999978 is 87999916.

61999978 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in only one way, i.e., 36929929 + 25070049 = 6077^2 + 5007^2 .

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15499993 + ... + 15499996.

Almost surely, 2^61999978 is an apocalyptic number.

61999978 is a deficient number, since it is larger than the sum of its proper divisors (30999992).

61999978 is a wasteful number, since it uses less digits than its factorization.

61999978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30999991.

The product of its digits is 2204496, while the sum is 58.

The square root of 61999978 is about 7874.0064770103. The cubic root of 61999978 is about 395.7891141543.

The spelling of 61999978 in words is "sixty-one million, nine hundred ninety-nine thousand, nine hundred seventy-eight".