61991638 has 16 divisors (see below), whose sum is σ = 95705280. Its totient is φ = 30098376.

The previous prime is 61991603. The next prime is 61991641. The reversal of 61991638 is 83619916.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is a junction number, because it is equal to n+sod(n) for n = 61991594 and 61991603.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13381 + ... + 17407.

It is an arithmetic number, because the mean of its divisors is an integer number (5981580).

Almost surely, 2^61991638 is an apocalyptic number.

61991638 is a deficient number, since it is larger than the sum of its proper divisors (33713642).

61991638 is a wasteful number, since it uses less digits than its factorization.

61991638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4251.

The product of its digits is 69984, while the sum is 43.

The square root of 61991638 is about 7873.4768685759. The cubic root of 61991638 is about 395.7713666790.

The spelling of 61991638 in words is "sixty-one million, nine hundred ninety-one thousand, six hundred thirty-eight".