21651164 has 6 divisors (see below), whose sum is σ = 37889544. Its totient is φ = 10825580.

The previous prime is 21651163. The next prime is 21651167. The reversal of 21651164 is 46115612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21651163) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2706392 + ... + 2706399.

It is an arithmetic number, because the mean of its divisors is an integer number (6314924).

Almost surely, 2^21651164 is an apocalyptic number.

It is an amenable number.

21651164 is a deficient number, since it is larger than the sum of its proper divisors (16238380).

21651164 is a wasteful number, since it uses less digits than its factorization.

21651164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5412795 (or 5412793 counting only the distinct ones).

The product of its digits is 1440, while the sum is 26.

The square root of 21651164 is about 4653.0811297462. The cubic root of 21651164 is about 278.7150475993.

Adding to 21651164 its reverse (46115612), we get a palindrome (67766776).

The spelling of 21651164 in words is "twenty-one million, six hundred fifty-one thousand, one hundred sixty-four".