20155201561 has 4 divisors (see below), whose sum is σ = 21987492624. Its totient is φ = 18322910500.

The previous prime is 20155201537. The next prime is 20155201597. The reversal of 20155201561 is 16510255102.

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 20155201561 - 2⁵ = 20155201529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20155201511) 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, 916145515 + ... + 916145536.

It is an arithmetic number, because the mean of its divisors is an integer number (5496873156).

Almost surely, 2^20155201561 is an apocalyptic number.

It is an amenable number.

20155201561 is a deficient number, since it is larger than the sum of its proper divisors (1832291063).

20155201561 is a wasteful number, since it uses less digits than its factorization.

20155201561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1832291062.

The product of its (nonzero) digits is 3000, while the sum is 28.

Adding to 20155201561 its reverse (16510255102), we get a palindrome (36665456663).

The spelling of 20155201561 in words is "twenty billion, one hundred fifty-five million, two hundred one thousand, five hundred sixty-one".