21587945 has 8 divisors (see below), whose sum is σ = 25940736. Its totient is φ = 17246896.

The previous prime is 21587941. The next prime is 21587959. The reversal of 21587945 is 54978512.

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 21587945 - 2² = 21587941 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21587941) 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, 1814 + ... + 6816.

It is an arithmetic number, because the mean of its divisors is an integer number (3242592).

Almost surely, 2^21587945 is an apocalyptic number.

It is an amenable number.

21587945 is a deficient number, since it is larger than the sum of its proper divisors (4352791).

21587945 is an equidigital number, since it uses as much as digits as its factorization.

21587945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5871.

The product of its digits is 100800, while the sum is 41.

The square root of 21587945 is about 4646.2829229396. The cubic root of 21587945 is about 278.4435107890.

It can be divided in two parts, 215 and 87945, that multiplied together give a triangular number (18908175 = T₆₁₄₉).

The spelling of 21587945 in words is "twenty-one million, five hundred eighty-seven thousand, nine hundred forty-five".