20161551 has 4 divisors (see below), whose sum is σ = 26882072. Its totient is φ = 13441032.

The previous prime is 20161549. The next prime is 20161553. The reversal of 20161551 is 15516102.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (20161549) and next prime (20161553).

It is not a de Polignac number, because 20161551 - 2¹ = 20161549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20161553) 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, 3360256 + ... + 3360261.

It is an arithmetic number, because the mean of its divisors is an integer number (6720518).

Almost surely, 2^20161551 is an apocalyptic number.

20161551 is a deficient number, since it is larger than the sum of its proper divisors (6720521).

20161551 is an equidigital number, since it uses as much as digits as its factorization.

20161551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6720520.

The product of its (nonzero) digits is 300, while the sum is 21.

The square root of 20161551 is about 4490.1615783845. The cubic root of 20161551 is about 272.1706640536.

Adding to 20161551 its reverse (15516102), we get a palindrome (35677653).

The spelling of 20161551 in words is "twenty million, one hundred sixty-one thousand, five hundred fifty-one".