21640330 has 16 divisors (see below), whose sum is σ = 39535200. Its totient is φ = 8526672.

The previous prime is 21640279. The next prime is 21640331. The reversal of 21640330 is 3304612.

It is a junction number, because it is equal to n+sod(n) for n = 21640298 and 21640307.

It is not an unprimeable number, because it can be changed into a prime (21640331) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15480 + ... + 16819.

It is an arithmetic number, because the mean of its divisors is an integer number (2470950).

Almost surely, 2^21640330 is an apocalyptic number.

21640330 is a deficient number, since it is larger than the sum of its proper divisors (17894870).

21640330 is a wasteful number, since it uses less digits than its factorization.

21640330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32373.

The product of its (nonzero) digits is 432, while the sum is 19.

The square root of 21640330 is about 4651.9168092304. The cubic root of 21640330 is about 278.6685512134.

Adding to 21640330 its reverse (3304612), we get a palindrome (24944942).

The spelling of 21640330 in words is "twenty-one million, six hundred forty thousand, three hundred thirty".