21640801 has 24 divisors (see below), whose sum is σ = 27665064. Its totient is φ = 16773120.

The previous prime is 21640789. The next prime is 21640811. The reversal of 21640801 is 10804612.

It can be written as a sum of positive squares in 4 ways, for example, as 5832225 + 15808576 = 2415^2 + 3976^2 .

It is not a de Polignac number, because 21640801 - 2¹³ = 21632609 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21640811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33441 + ... + 34081.

It is an arithmetic number, because the mean of its divisors is an integer number (1152711).

Almost surely, 2^21640801 is an apocalyptic number.

It is an amenable number.

21640801 is a deficient number, since it is larger than the sum of its proper divisors (6024263).

21640801 is a wasteful number, since it uses less digits than its factorization.

21640801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 721 (or 714 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 21640801 is about 4651.9674332480. The cubic root of 21640801 is about 278.6705729315.

The spelling of 21640801 in words is "twenty-one million, six hundred forty thousand, eight hundred one".