21072578 has 4 divisors (see below), whose sum is σ = 31608870. Its totient is φ = 10536288.

The previous prime is 21072559. The next prime is 21072581. The reversal of 21072578 is 87527012.

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., 13712209 + 7360369 = 3703^2 + 2713^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5268143 + ... + 5268146.

Almost surely, 2^21072578 is an apocalyptic number.

21072578 is a deficient number, since it is larger than the sum of its proper divisors (10536292).

21072578 is a wasteful number, since it uses less digits than its factorization.

21072578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10536291.

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 21072578 is about 4590.4877736467. The cubic root of 21072578 is about 276.2098890050.

The spelling of 21072578 in words is "twenty-one million, seventy-two thousand, five hundred seventy-eight".