61721581 has 8 divisors (see below), whose sum is σ = 64525824. Its totient is φ = 58927440.

The previous prime is 61721563. The next prime is 61721603. The reversal of 61721581 is 18512716.

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

It is a cyclic number.

It is not a de Polignac number, because 61721581 - 2⁵ = 61721549 is a prime.

It is a super-2 number, since 2×61721581² = 7619107122279122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61721501) 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, 11751 + ... + 16171.

It is an arithmetic number, because the mean of its divisors is an integer number (8065728).

Almost surely, 2^61721581 is an apocalyptic number.

It is an amenable number.

61721581 is a deficient number, since it is larger than the sum of its proper divisors (2804243).

61721581 is a wasteful number, since it uses less digits than its factorization.

61721581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5051.

The product of its digits is 3360, while the sum is 31.

The square root of 61721581 is about 7856.3083569829. The cubic root of 61721581 is about 395.1958244961.

The spelling of 61721581 in words is "sixty-one million, seven hundred twenty-one thousand, five hundred eighty-one".