21640270 has 16 divisors (see below), whose sum is σ = 39005568. Its totient is φ = 8644320.

The previous prime is 21640249. The next prime is 21640273. The reversal of 21640270 is 7204612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640273) 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, 13027 + ... + 14593.

It is an arithmetic number, because the mean of its divisors is an integer number (2437848).

Almost surely, 2^21640270 is an apocalyptic number.

21640270 is a deficient number, since it is larger than the sum of its proper divisors (17365298).

21640270 is a wasteful number, since it uses less digits than its factorization.

21640270 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2955.

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 21640270 is about 4651.9103602714. The cubic root of 21640270 is about 278.6682936676.

Adding to 21640270 its reverse (7204612), we get a palindrome (28844882).

The spelling of 21640270 in words is "twenty-one million, six hundred forty thousand, two hundred seventy".