21861545 has 8 divisors (see below), whose sum is σ = 26466696. Its totient is φ = 17334016.

The previous prime is 21861517. The next prime is 21861547. The reversal of 21861545 is 54516812.

It can be written as a sum of positive squares in 4 ways, for example, as 811801 + 21049744 = 901^2 + 4588^2 .

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 21861545 - 2⁶ = 21861481 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21861547) 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, 18782 + ... + 19911.

It is an arithmetic number, because the mean of its divisors is an integer number (3308337).

Almost surely, 2^21861545 is an apocalyptic number.

It is an amenable number.

21861545 is a deficient number, since it is larger than the sum of its proper divisors (4605151).

21861545 is a wasteful number, since it uses less digits than its factorization.

21861545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38811.

The product of its digits is 9600, while the sum is 32.

The square root of 21861545 is about 4675.6331122106. The cubic root of 21861545 is about 279.6148829609.

The spelling of 21861545 in words is "twenty-one million, eight hundred sixty-one thousand, five hundred forty-five".