21640508 has 6 divisors (see below), whose sum is σ = 37870896. Its totient is φ = 10820252.

The previous prime is 21640501. The next prime is 21640513. The reversal of 21640508 is 80504612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2705060 + ... + 2705067.

It is an arithmetic number, because the mean of its divisors is an integer number (6311816).

Almost surely, 2^21640508 is an apocalyptic number.

It is an amenable number.

21640508 is a deficient number, since it is larger than the sum of its proper divisors (16230388).

21640508 is a wasteful number, since it uses less digits than its factorization.

21640508 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5410131 (or 5410129 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21640508 is about 4651.9359410895. The cubic root of 21640508 is about 278.6693152632.

The spelling of 21640508 in words is "twenty-one million, six hundred forty thousand, five hundred eight".