21390830 has 16 divisors (see below), whose sum is σ = 38992320. Its totient is φ = 8447712.

The previous prime is 21390797. The next prime is 21390833. The reversal of 21390830 is 3809312.

It is a self number, because there is not a number n which added to its sum of digits gives 21390830.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390833) 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, 12749 + ... + 14328.

It is an arithmetic number, because the mean of its divisors is an integer number (2437020).

Almost surely, 2^21390830 is an apocalyptic number.

21390830 is a deficient number, since it is larger than the sum of its proper divisors (17601490).

21390830 is a wasteful number, since it uses less digits than its factorization.

21390830 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27163.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 21390830 is about 4625.0221621091. The cubic root of 21390830 is about 277.5934484940.

The spelling of 21390830 in words is "twenty-one million, three hundred ninety thousand, eight hundred thirty".