21861307 has 4 divisors (see below), whose sum is σ = 23542960. Its totient is φ = 20179656.

The previous prime is 21861283. The next prime is 21861311. The reversal of 21861307 is 70316812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21861307 - 2⁷ = 21861179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21861377) 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, 840807 + ... + 840832.

It is an arithmetic number, because the mean of its divisors is an integer number (5885740).

Almost surely, 2^21861307 is an apocalyptic number.

21861307 is a deficient number, since it is larger than the sum of its proper divisors (1681653).

21861307 is a wasteful number, since it uses less digits than its factorization.

21861307 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1681652.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21861307 is about 4675.6076610426. The cubic root of 21861307 is about 279.6138682631.

It can be divided in two parts, 21 and 861307, that added together give a triangular number (861328 = T₁₃₁₂).

The spelling of 21861307 in words is "twenty-one million, eight hundred sixty-one thousand, three hundred seven".