21553161 has 16 divisors (see below), whose sum is σ = 34775424. Its totient is φ = 11591424.

The previous prime is 21553157. The next prime is 21553183. The reversal of 21553161 is 16135512.

It is not a de Polignac number, because 21553161 - 2² = 21553157 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21553111) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29830 + ... + 30543.

It is an arithmetic number, because the mean of its divisors is an integer number (2173464).

Almost surely, 2^21553161 is an apocalyptic number.

21553161 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21553161 is a deficient number, since it is larger than the sum of its proper divisors (13222263).

21553161 is a wasteful number, since it uses less digits than its factorization.

21553161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60400.

The product of its digits is 900, while the sum is 24.

The square root of 21553161 is about 4642.5382066279. The cubic root of 21553161 is about 278.2938812054.

Adding to 21553161 its reverse (16135512), we get a palindrome (37688673).

The spelling of 21553161 in words is "twenty-one million, five hundred fifty-three thousand, one hundred sixty-one".