21500978 has 4 divisors (see below), whose sum is σ = 32251470. Its totient is φ = 10750488.

The previous prime is 21500953. The next prime is 21501023. The reversal of 21500978 is 87900512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20948929 + 552049 = 4577^2 + 743^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5375243 + ... + 5375246.

Almost surely, 2^21500978 is an apocalyptic number.

21500978 is a deficient number, since it is larger than the sum of its proper divisors (10750492).

21500978 is a wasteful number, since it uses less digits than its factorization.

21500978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10750491.

The product of its (nonzero) digits is 5040, while the sum is 32.

The square root of 21500978 is about 4636.9147070008. The cubic root of 21500978 is about 278.0691045018.

The spelling of 21500978 in words is "twenty-one million, five hundred thousand, nine hundred seventy-eight".