21078545 has 8 divisors (see below), whose sum is σ = 25325160. Its totient is φ = 16842240.

The previous prime is 21078527. The next prime is 21078559. The reversal of 21078545 is 54587012.

It can be written as a sum of positive squares in 4 ways, for example, as 3041536 + 18037009 = 1744^2 + 4247^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21078545 - 2⁸ = 21078289 is a prime.

It is an alternating number because its digits alternate between even and odd.

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, 3041 + ... + 7169.

It is an arithmetic number, because the mean of its divisors is an integer number (3165645).

Almost surely, 2^21078545 is an apocalyptic number.

It is an amenable number.

21078545 is a deficient number, since it is larger than the sum of its proper divisors (4246615).

21078545 is a wasteful number, since it uses less digits than its factorization.

21078545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5155.

The product of its (nonzero) digits is 11200, while the sum is 32.

The square root of 21078545 is about 4591.1376585766. The cubic root of 21078545 is about 276.2359574634.

The spelling of 21078545 in words is "twenty-one million, seventy-eight thousand, five hundred forty-five".