51661209621 has 8 divisors (see below), whose sum is σ = 78721843264. Its totient is φ = 29520691200.

The previous prime is 51661209571. The next prime is 51661209647. The reversal of 51661209621 is 12690216615.

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

It is not a de Polignac number, because 51661209621 - 2⁶ = 51661209557 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 51661209621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51661209661) 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, 1230028780 + ... + 1230028821.

It is an arithmetic number, because the mean of its divisors is an integer number (9840230408).

Almost surely, 2^51661209621 is an apocalyptic number.

It is an amenable number.

51661209621 is a deficient number, since it is larger than the sum of its proper divisors (27060633643).

51661209621 is a wasteful number, since it uses less digits than its factorization.

51661209621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2460057611.

The product of its (nonzero) digits is 38880, while the sum is 39.

The spelling of 51661209621 in words is "fifty-one billion, six hundred sixty-one million, two hundred nine thousand, six hundred twenty-one".