61531721 has 8 divisors (see below), whose sum is σ = 65447424. Its totient is φ = 57648960.

The previous prime is 61531697. The next prime is 61531727. The reversal of 61531721 is 12713516.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-61531721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61531727) 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, 4325 + ... + 11906.

It is an arithmetic number, because the mean of its divisors is an integer number (8180928).

Almost surely, 2^61531721 is an apocalyptic number.

It is an amenable number.

61531721 is a deficient number, since it is larger than the sum of its proper divisors (3915703).

61531721 is a wasteful number, since it uses less digits than its factorization.

61531721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16471.

The product of its digits is 1260, while the sum is 26.

The square root of 61531721 is about 7844.2157670477. The cubic root of 61531721 is about 394.7901914137.

The spelling of 61531721 in words is "sixty-one million, five hundred thirty-one thousand, seven hundred twenty-one".