21399830 has 16 divisors (see below), whose sum is σ = 38593584. Its totient is φ = 8543520.

The previous prime is 21399823. The next prime is 21399839. The reversal of 21399830 is 3899312.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21399839) 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, 4385 + ... + 7875.

It is an arithmetic number, because the mean of its divisors is an integer number (2412099).

Almost surely, 2^21399830 is an apocalyptic number.

21399830 is a deficient number, since it is larger than the sum of its proper divisors (17193754).

21399830 is a wasteful number, since it uses less digits than its factorization.

21399830 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4111.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 21399830 is about 4625.9950280994. The cubic root of 21399830 is about 277.6323746871.

The spelling of 21399830 in words is "twenty-one million, three hundred ninety-nine thousand, eight hundred thirty".