61691639 has 4 divisors (see below), whose sum is σ = 62737320. Its totient is φ = 60645960.

The previous prime is 61691621. The next prime is 61691701. The reversal of 61691639 is 93619616.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61691639 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 61691596 and 61691605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61691239) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 522752 + ... + 522869.

It is an arithmetic number, because the mean of its divisors is an integer number (15684330).

Almost surely, 2^61691639 is an apocalyptic number.

61691639 is a deficient number, since it is larger than the sum of its proper divisors (1045681).

61691639 is a wasteful number, since it uses less digits than its factorization.

61691639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1045680.

The product of its digits is 52488, while the sum is 41.

The square root of 61691639 is about 7854.4025234260. The cubic root of 61691639 is about 395.1319091570.

The spelling of 61691639 in words is "sixty-one million, six hundred ninety-one thousand, six hundred thirty-nine".