661721069 has 8 divisors (see below), whose sum is σ = 674200800. Its totient is φ = 649348816.

The previous prime is 661721041. The next prime is 661721087. The reversal of 661721069 is 960127166.

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 661721069 - 2²⁴ = 644943853 is a prime.

It is a super-2 number, since 2×661721069² = 875749546317005522, 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 (661721029) 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, 14387 + ... + 39120.

It is an arithmetic number, because the mean of its divisors is an integer number (84275100).

Almost surely, 2^661721069 is an apocalyptic number.

It is an amenable number.

661721069 is a deficient number, since it is larger than the sum of its proper divisors (12479731).

661721069 is a wasteful number, since it uses less digits than its factorization.

661721069 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53739.

The product of its (nonzero) digits is 27216, while the sum is 38.

The square root of 661721069 is about 25723.9396088546. The cubic root of 661721069 is about 871.4149121456.

The spelling of 661721069 in words is "six hundred sixty-one million, seven hundred twenty-one thousand, sixty-nine".