21356987 has 8 divisors (see below), whose sum is σ = 21829632. Its totient is φ = 20889000.

The previous prime is 21356983. The next prime is 21356989. The reversal of 21356987 is 78965312.

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 21356987 - 2² = 21356983 is a prime.

It is a super-2 number, since 2×21356987² = 912241787436338, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21356983) 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, 9062 + ... + 11172.

It is an arithmetic number, because the mean of its divisors is an integer number (2728704).

Almost surely, 2^21356987 is an apocalyptic number.

21356987 is a deficient number, since it is larger than the sum of its proper divisors (472645).

21356987 is a wasteful number, since it uses less digits than its factorization.

21356987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2329.

The product of its digits is 90720, while the sum is 41.

The square root of 21356987 is about 4621.3620286664. The cubic root of 21356987 is about 277.4469752324.

The spelling of 21356987 in words is "twenty-one million, three hundred fifty-six thousand, nine hundred eighty-seven".