21678413 has 4 divisors (see below), whose sum is σ = 21708960. Its totient is φ = 21647868.

The previous prime is 21678401. The next prime is 21678427. The reversal of 21678413 is 31487612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21678413 - 2¹⁰ = 21677389 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21678413.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21678313) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14183 + ... + 15636.

It is an arithmetic number, because the mean of its divisors is an integer number (5427240).

Almost surely, 2^21678413 is an apocalyptic number.

It is an amenable number.

21678413 is a deficient number, since it is larger than the sum of its proper divisors (30547).

21678413 is an equidigital number, since it uses as much as digits as its factorization.

21678413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30546.

The product of its digits is 8064, while the sum is 32.

The square root of 21678413 is about 4656.0082688930. The cubic root of 21678413 is about 278.8319238784.

The spelling of 21678413 in words is "twenty-one million, six hundred seventy-eight thousand, four hundred thirteen".