21365646 has 16 divisors (see below), whose sum is σ = 42989184. Its totient is φ = 7078904.

The previous prime is 21365623. The next prime is 21365647. The reversal of 21365646 is 64656312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365647) 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, 9660 + ... + 11663.

It is an arithmetic number, because the mean of its divisors is an integer number (2686824).

Almost surely, 2^21365646 is an apocalyptic number.

21365646 is an abundant number, since it is smaller than the sum of its proper divisors (21623538).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21365646 is a wasteful number, since it uses less digits than its factorization.

21365646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21495.

The product of its digits is 25920, while the sum is 33.

The square root of 21365646 is about 4622.2987787464. The cubic root of 21365646 is about 277.4844663004.

The spelling of 21365646 in words is "twenty-one million, three hundred sixty-five thousand, six hundred forty-six".