21355986 has 16 divisors (see below), whose sum is σ = 42757344. Its totient is φ = 7111104.

The previous prime is 21355969. The next prime is 21355987. The reversal of 21355986 is 68955312.

It is not an unprimeable number, because it can be changed into a prime (21355987) 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, 9661 + ... + 11663.

It is an arithmetic number, because the mean of its divisors is an integer number (2672334).

Almost surely, 2^21355986 is an apocalyptic number.

21355986 is an abundant number, since it is smaller than the sum of its proper divisors (21401358).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21355986 is a wasteful number, since it uses less digits than its factorization.

21355986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3785.

The product of its digits is 64800, while the sum is 39.

The square root of 21355986 is about 4621.2537259925. The cubic root of 21355986 is about 277.4426405267.

The spelling of 21355986 in words is "twenty-one million, three hundred fifty-five thousand, nine hundred eighty-six".