61517721 has 8 divisors (see below), whose sum is σ = 82108960. Its totient is φ = 40969152.

The previous prime is 61517719. The next prime is 61517723. The reversal of 61517721 is 12771516.

It is an interprime number because it is at equal distance from previous prime (61517719) and next prime (61517723).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 61517721 - 2¹ = 61517719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61517723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7135 + ... + 13188.

It is an arithmetic number, because the mean of its divisors is an integer number (10263620).

Almost surely, 2^61517721 is an apocalyptic number.

It is an amenable number.

61517721 is a deficient number, since it is larger than the sum of its proper divisors (20591239).

61517721 is a wasteful number, since it uses less digits than its factorization.

61517721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21335.

The product of its digits is 2940, while the sum is 30.

The square root of 61517721 is about 7843.3233389935. The cubic root of 61517721 is about 394.7602476068.

It can be divided in two parts, 615 and 17721, that added together give a triangular number (18336 = T₁₉₁).

The spelling of 61517721 in words is "sixty-one million, five hundred seventeen thousand, seven hundred twenty-one".