61512721 has 4 divisors (see below), whose sum is σ = 61687332. Its totient is φ = 61338112.

The previous prime is 61512673. The next prime is 61512727. The reversal of 61512721 is 12721516.

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

It can be written as a sum of positive squares in 2 ways, for example, as 34680321 + 26832400 = 5889^2 + 5180^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61512721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61512727) 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, 86776 + ... + 87481.

It is an arithmetic number, because the mean of its divisors is an integer number (15421833).

Almost surely, 2^61512721 is an apocalyptic number.

It is an amenable number.

61512721 is a deficient number, since it is larger than the sum of its proper divisors (174611).

61512721 is a wasteful number, since it uses less digits than its factorization.

61512721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174610.

The product of its digits is 840, while the sum is 25.

The square root of 61512721 is about 7843.0045900790. The cubic root of 61512721 is about 394.7495522891.

The spelling of 61512721 in words is "sixty-one million, five hundred twelve thousand, seven hundred twenty-one".