61721881 has 8 divisors (see below), whose sum is σ = 66895304. Its totient is φ = 56609280.

The previous prime is 61721867. The next prime is 61721897. The reversal of 61721881 is 18812716.

It can be written as a sum of positive squares in 4 ways, for example, as 632025 + 61089856 = 795^2 + 7816^2 .

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

It is not a de Polignac number, because 61721881 - 2¹⁵ = 61689113 is a prime.

It is a super-2 number, since 2×61721881² = 7619181188356322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61721381) 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, 13080 + ... + 17161.

It is an arithmetic number, because the mean of its divisors is an integer number (8361913).

Almost surely, 2^61721881 is an apocalyptic number.

It is an amenable number.

61721881 is a deficient number, since it is larger than the sum of its proper divisors (5173423).

61721881 is a wasteful number, since it uses less digits than its factorization.

61721881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30411.

The product of its digits is 5376, while the sum is 34.

The square root of 61721881 is about 7856.3274498967. The cubic root of 61721881 is about 395.1964647830.

The spelling of 61721881 in words is "sixty-one million, seven hundred twenty-one thousand, eight hundred eighty-one".