21640367 has 4 divisors (see below), whose sum is σ = 24731856. Its totient is φ = 18548880.

The previous prime is 21640363. The next prime is 21640379. The reversal of 21640367 is 76304612.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21640367 - 2² = 21640363 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640363) 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 3 ways as a sum of consecutive naturals, for example, 1545734 + ... + 1545747.

It is an arithmetic number, because the mean of its divisors is an integer number (6182964).

Almost surely, 2^21640367 is an apocalyptic number.

21640367 is a deficient number, since it is larger than the sum of its proper divisors (3091489).

21640367 is an equidigital number, since it uses as much as digits as its factorization.

21640367 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3091488.

The product of its (nonzero) digits is 6048, while the sum is 29.

The square root of 21640367 is about 4651.9207860840. The cubic root of 21640367 is about 278.6687100331.

Adding to 21640367 its reverse (76304612), we get a palindrome (97944979).

The spelling of 21640367 in words is "twenty-one million, six hundred forty thousand, three hundred sixty-seven".