21345987 has 16 divisors (see below), whose sum is σ = 32264960. Its totient is φ = 12444192.

The previous prime is 21345983. The next prime is 21345997. The reversal of 21345987 is 78954312.

It is not a de Polignac number, because 21345987 - 2² = 21345983 is a prime.

It is a super-2 number, since 2×21345987² = 911302322008338, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is not an unprimeable number, because it can be changed into a prime (21345983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13663 + ... + 15144.

It is an arithmetic number, because the mean of its divisors is an integer number (2016560).

Almost surely, 2^21345987 is an apocalyptic number.

21345987 is a deficient number, since it is larger than the sum of its proper divisors (10918973).

21345987 is a wasteful number, since it uses less digits than its factorization.

21345987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28842.

The product of its digits is 60480, while the sum is 39.

The square root of 21345987 is about 4620.1717500543. The cubic root of 21345987 is about 277.3993336675.

The spelling of 21345987 in words is "twenty-one million, three hundred forty-five thousand, nine hundred eighty-seven".