21487861 has 8 divisors (see below), whose sum is σ = 22160384. Its totient is φ = 20820240.

The previous prime is 21487783. The next prime is 21487891. The reversal of 21487861 is 16878412.

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 21487861 - 2¹¹ = 21485813 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is the 4636-th Hogben number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21487861.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21487891) by changing a digit.

It is a nontrivial repunit in base 4635.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8956 + ... + 11098.

It is an arithmetic number, because the mean of its divisors is an integer number (2770048).

Almost surely, 2^21487861 is an apocalyptic number.

It is an amenable number.

21487861 is a deficient number, since it is larger than the sum of its proper divisors (672523).

21487861 is a wasteful number, since it uses less digits than its factorization.

21487861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2451.

The product of its digits is 21504, while the sum is 37.

The square root of 21487861 is about 4635.5000808974. The cubic root of 21487861 is about 278.0125462309.

The spelling of 21487861 in words is "twenty-one million, four hundred eighty-seven thousand, eight hundred sixty-one".