61139721 has 4 divisors (see below), whose sum is σ = 81519632. Its totient is φ = 40759812.

The previous prime is 61139677. The next prime is 61139731. The reversal of 61139721 is 12793116.

61139721 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, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 61139721 - 2¹⁵ = 61106953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61139731) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 10189951 + ... + 10189956.

It is an arithmetic number, because the mean of its divisors is an integer number (20379908).

Almost surely, 2^61139721 is an apocalyptic number.

It is an amenable number.

61139721 is a deficient number, since it is larger than the sum of its proper divisors (20379911).

61139721 is a wasteful number, since it uses less digits than its factorization.

61139721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20379910.

The product of its digits is 2268, while the sum is 30.

The square root of 61139721 is about 7819.1892802259. The cubic root of 61139721 is about 393.9500417645.

The spelling of 61139721 in words is "sixty-one million, one hundred thirty-nine thousand, seven hundred twenty-one".