21495778 has 4 divisors (see below), whose sum is σ = 32243670. Its totient is φ = 10747888.

The previous prime is 21495763. The next prime is 21495787. The reversal of 21495778 is 87759412.

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., 18861649 + 2634129 = 4343^2 + 1623^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5373943 + ... + 5373946.

Almost surely, 2^21495778 is an apocalyptic number.

21495778 is a deficient number, since it is larger than the sum of its proper divisors (10747892).

21495778 is a wasteful number, since it uses less digits than its factorization.

21495778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10747891.

The product of its digits is 141120, while the sum is 43.

The square root of 21495778 is about 4636.3539554266. The cubic root of 21495778 is about 278.0466857398.

The spelling of 21495778 in words is "twenty-one million, four hundred ninety-five thousand, seven hundred seventy-eight".