21861306 has 32 divisors (see below), whose sum is σ = 48734400. Its totient is φ = 7264080.

The previous prime is 21861283. The next prime is 21861311. The reversal of 21861306 is 60316812.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21861306.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30480 + ... + 31188.

It is an arithmetic number, because the mean of its divisors is an integer number (1522950).

Almost surely, 2^21861306 is an apocalyptic number.

21861306 is an abundant number, since it is smaller than the sum of its proper divisors (26873094).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21861306 is a wasteful number, since it uses less digits than its factorization.

21861306 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1291 (or 1285 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21861306 is about 4675.6075541046. The cubic root of 21861306 is about 279.6138639997.

The spelling of 21861306 in words is "twenty-one million, eight hundred sixty-one thousand, three hundred six".