61664681 has 8 divisors (see below), whose sum is σ = 68203464. Its totient is φ = 55382400.

The previous prime is 61664677. The next prime is 61664683. The reversal of 61664681 is 18646616.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 19219456 + 42445225 = 4384^2 + 6515^2 .

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 61664681 - 2² = 61664677 is a prime.

It is a super-4 number, since 4×61664681⁴ (a number of 32 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (61664683) 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, 63620 + ... + 64581.

It is an arithmetic number, because the mean of its divisors is an integer number (8525433).

Almost surely, 2^61664681 is an apocalyptic number.

It is an amenable number.

61664681 is a deficient number, since it is larger than the sum of its proper divisors (6538783).

61664681 is a wasteful number, since it uses less digits than its factorization.

61664681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128251.

The product of its digits is 41472, while the sum is 38.

The square root of 61664681 is about 7852.6862282916. The cubic root of 61664681 is about 395.0743458842.

The spelling of 61664681 in words is "sixty-one million, six hundred sixty-four thousand, six hundred eighty-one".