21612805 has 8 divisors (see below), whose sum is σ = 26033400. Its totient is φ = 17224896.

The previous prime is 21612769. The next prime is 21612827. The reversal of 21612805 is 50821612.

It can be written as a sum of positive squares in 4 ways, for example, as 101761 + 21511044 = 319^2 + 4638^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21612805 - 2⁷ = 21612677 is a prime.

It is a super-2 number, since 2×21612805² = 934226679936050, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21612805.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6690 + ... + 9379.

It is an arithmetic number, because the mean of its divisors is an integer number (3254175).

Almost surely, 2^21612805 is an apocalyptic number.

It is an amenable number.

21612805 is a deficient number, since it is larger than the sum of its proper divisors (4420595).

21612805 is a wasteful number, since it uses less digits than its factorization.

21612805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16343.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21612805 is about 4648.9574100007. The cubic root of 21612805 is about 278.5503520575.

The spelling of 21612805 in words is "twenty-one million, six hundred twelve thousand, eight hundred five".