21640161 has 16 divisors (see below), whose sum is σ = 29445120. Its totient is φ = 14133840.

The previous prime is 21640147. The next prime is 21640181. The reversal of 21640161 is 16104612.

It is a de Polignac number, because none of the positive numbers 2^k-21640161 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21640121) 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, 60100 + ... + 60458.

It is an arithmetic number, because the mean of its divisors is an integer number (1840320).

Almost surely, 2^21640161 is an apocalyptic number.

It is an amenable number.

21640161 is a deficient number, since it is larger than the sum of its proper divisors (7804959).

21640161 is a wasteful number, since it uses less digits than its factorization.

21640161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 716.

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 21640161 is about 4651.8986446396. The cubic root of 21640161 is about 278.6678257915.

Adding to 21640161 its reverse (16104612), we get a palindrome (37744773).

The spelling of 21640161 in words is "twenty-one million, six hundred forty thousand, one hundred sixty-one".