20621561755 has 8 divisors (see below), whose sum is σ = 24746902992. Its totient is φ = 16496563488.

The previous prime is 20621561717. The next prime is 20621561771. The reversal of 20621561755 is 55716512602.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20621561755 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73392 + ... + 215938.

It is an arithmetic number, because the mean of its divisors is an integer number (3093362874).

Almost surely, 2^20621561755 is an apocalyptic number.

20621561755 is a deficient number, since it is larger than the sum of its proper divisors (4125341237).

20621561755 is a wasteful number, since it uses less digits than its factorization.

20621561755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171485.

The product of its (nonzero) digits is 126000, while the sum is 40.

The spelling of 20621561755 in words is "twenty billion, six hundred twenty-one million, five hundred sixty-one thousand, seven hundred fifty-five".