21649164 has 24 divisors (see below), whose sum is σ = 52711680. Its totient is φ = 6902544.

The previous prime is 21649163. The next prime is 21649169. The reversal of 21649164 is 46194612.

Added to its reverse (46194612) it gives a triangular number (67843776 = T₁₁₆₄₈).

It is not an unprimeable number, because it can be changed into a prime (21649163) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 38944 + ... + 39495.

It is an arithmetic number, because the mean of its divisors is an integer number (2196320).

Almost surely, 2^21649164 is an apocalyptic number.

It is an amenable number.

21649164 is an abundant number, since it is smaller than the sum of its proper divisors (31062516).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21649164 is a wasteful number, since it uses less digits than its factorization.

21649164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78469 (or 78467 counting only the distinct ones).

The product of its digits is 10368, while the sum is 33.

The square root of 21649164 is about 4652.8662134216. The cubic root of 21649164 is about 278.7064653469.

Adding to 21649164 its reverse (46194612), we get a triangular number (67843776 = T₁₁₆₄₈).

The spelling of 21649164 in words is "twenty-one million, six hundred forty-nine thousand, one hundred sixty-four".