21640479 has 16 divisors (see below), whose sum is σ = 33047040. Its totient is φ = 12339360.

The previous prime is 21640477. The next prime is 21640499. The reversal of 21640479 is 97404612.

It is a happy number.

It is not a de Polignac number, because 21640479 - 2¹ = 21640477 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640471) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13102 + ... + 14660.

It is an arithmetic number, because the mean of its divisors is an integer number (2065440).

Almost surely, 2^21640479 is an apocalyptic number.

21640479 is a deficient number, since it is larger than the sum of its proper divisors (11406561).

21640479 is a wasteful number, since it uses less digits than its factorization.

21640479 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2230.

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 21640479 is about 4651.9328241066. The cubic root of 21640479 is about 278.6691907835.

The spelling of 21640479 in words is "twenty-one million, six hundred forty thousand, four hundred seventy-nine".