21206161 has 8 divisors (see below), whose sum is σ = 22264704. Its totient is φ = 20159040.

The previous prime is 21206131. The next prime is 21206173. The reversal of 21206161 is 16160212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21206161 - 2⁹ = 21205649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21206131) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1081 + ... + 6601.

It is an arithmetic number, because the mean of its divisors is an integer number (2783088).

Almost surely, 2^21206161 is an apocalyptic number.

It is an amenable number.

21206161 is a deficient number, since it is larger than the sum of its proper divisors (1058543).

21206161 is a wasteful number, since it uses less digits than its factorization.

21206161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5711.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21206161 is about 4605.0147665344. The cubic root of 21206161 is about 276.7923087021.

Adding to 21206161 its reverse (16160212), we get a palindrome (37366373).

It can be divided in two parts, 2120 and 6161, that added together give a square (8281 = 91²).

The spelling of 21206161 in words is "twenty-one million, two hundred six thousand, one hundred sixty-one".