21440987 has 8 divisors (see below), whose sum is σ = 22794960. Its totient is φ = 20109600.

The previous prime is 21440941. The next prime is 21440989. The reversal of 21440987 is 78904412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21440987 - 2¹⁰ = 21439963 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is not an unprimeable number, because it can be changed into a prime (21440989) 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, 3668 + ... + 7505.

It is an arithmetic number, because the mean of its divisors is an integer number (2849370).

Almost surely, 2^21440987 is an apocalyptic number.

21440987 is a deficient number, since it is larger than the sum of its proper divisors (1353973).

21440987 is a wasteful number, since it uses less digits than its factorization.

21440987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11293.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21440987 is about 4630.4413396565. The cubic root of 21440987 is about 277.8102452301.

The spelling of 21440987 in words is "twenty-one million, four hundred forty thousand, nine hundred eighty-seven".