21407805 has 12 divisors (see below), whose sum is σ = 37106940. Its totient is φ = 11417472.

The previous prime is 21407801. The next prime is 21407809. The reversal of 21407805 is 50870412.

It is an interprime number because it is at equal distance from previous prime (21407801) and next prime (21407809).

It can be written as a sum of positive squares in 2 ways, for example, as 10478169 + 10929636 = 3237^2 + 3306^2 .

It is not a de Polignac number, because 21407805 - 2² = 21407801 is a prime.

It is a super-2 number, since 2×21407805² = 916588229836050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21407801) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 237820 + ... + 237909.

It is an arithmetic number, because the mean of its divisors is an integer number (3092245).

Almost surely, 2^21407805 is an apocalyptic number.

It is an amenable number.

21407805 is a deficient number, since it is larger than the sum of its proper divisors (15699135).

21407805 is a wasteful number, since it uses less digits than its factorization.

21407805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 475740 (or 475737 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21407805 is about 4626.8569245223. The cubic root of 21407805 is about 277.6668585000. Note that the first 3 decimals are identical.

The spelling of 21407805 in words is "twenty-one million, four hundred seven thousand, eight hundred five".