21735978 has 16 divisors (see below), whose sum is σ = 47424096. Its totient is φ = 6586640.

The previous prime is 21735937. The next prime is 21736003. The reversal of 21735978 is 87953712.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 164601 + ... + 164732.

It is an arithmetic number, because the mean of its divisors is an integer number (2964006).

Almost surely, 2^21735978 is an apocalyptic number.

21735978 is an abundant number, since it is smaller than the sum of its proper divisors (25688118).

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

21735978 is a wasteful number, since it uses less digits than its factorization.

21735978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 329349.

The product of its digits is 105840, while the sum is 42.

The square root of 21735978 is about 4662.1859679768. The cubic root of 21735978 is about 279.0785097846.

The spelling of 21735978 in words is "twenty-one million, seven hundred thirty-five thousand, nine hundred seventy-eight".