20605987581 has 4 divisors (see below), whose sum is σ = 27474650112. Its totient is φ = 13737325052.

The previous prime is 20605987541. The next prime is 20605987603. The reversal of 20605987581 is 18578950602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20605987581 - 2³³ = 12016052989 is a prime.

It is a super-2 number, since 2×20605987581² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20605987541) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3434331261 + ... + 3434331266.

It is an arithmetic number, because the mean of its divisors is an integer number (6868662528).

Almost surely, 2^20605987581 is an apocalyptic number.

It is an amenable number.

20605987581 is a deficient number, since it is larger than the sum of its proper divisors (6868662531).

20605987581 is an equidigital number, since it uses as much as digits as its factorization.

20605987581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6868662530.

The product of its (nonzero) digits is 1209600, while the sum is 51.

The spelling of 20605987581 in words is "twenty billion, six hundred five million, nine hundred eighty-seven thousand, five hundred eighty-one".