21642987 has 8 divisors (see below), whose sum is σ = 29143440. Its totient is φ = 14285600.

The previous prime is 21642979. The next prime is 21643009. The reversal of 21642987 is 78924612.

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 21642987 - 2³ = 21642979 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21642937) 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, 35412 + ... + 36017.

It is an arithmetic number, because the mean of its divisors is an integer number (3642930).

Almost surely, 2^21642987 is an apocalyptic number.

21642987 is a deficient number, since it is larger than the sum of its proper divisors (7500453).

21642987 is a wasteful number, since it uses less digits than its factorization.

21642987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71533.

The product of its digits is 48384, while the sum is 39.

The square root of 21642987 is about 4652.2023816683. The cubic root of 21642987 is about 278.6799557228.

It can be divided in two parts, 2164 and 2987, that added together give a triangular number (5151 = T₁₀₁).

The spelling of 21642987 in words is "twenty-one million, six hundred forty-two thousand, nine hundred eighty-seven".