20421136555 has 8 divisors (see below), whose sum is σ = 24568362000. Its totient is φ = 16294910496.

The previous prime is 20421136517. The next prime is 20421136613. The reversal of 20421136555 is 55563112402.

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 20421136555 - 2²³ = 20412747947 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20421136555.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5247705 + ... + 5251594.

It is an arithmetic number, because the mean of its divisors is an integer number (3071045250).

Almost surely, 2^20421136555 is an apocalyptic number.

20421136555 is a deficient number, since it is larger than the sum of its proper divisors (4147225445).

20421136555 is a wasteful number, since it uses less digits than its factorization.

20421136555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10499693.

The product of its (nonzero) digits is 36000, while the sum is 34.

Adding to 20421136555 its reverse (55563112402), we get a palindrome (75984248957).

The spelling of 20421136555 in words is "twenty billion, four hundred twenty-one million, one hundred thirty-six thousand, five hundred fifty-five".