21264578 has 4 divisors (see below), whose sum is σ = 31896870. Its totient is φ = 10632288.

The previous prime is 21264577. The next prime is 21264583. The reversal of 21264578 is 87546212.

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., 13010449 + 8254129 = 3607^2 + 2873^2 .

It is not an unprimeable number, because it can be changed into a prime (21264577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5316143 + ... + 5316146.

Almost surely, 2^21264578 is an apocalyptic number.

21264578 is a deficient number, since it is larger than the sum of its proper divisors (10632292).

21264578 is a wasteful number, since it uses less digits than its factorization.

21264578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10632291.

The product of its digits is 26880, while the sum is 35.

The square root of 21264578 is about 4611.3531636603. The cubic root of 21264578 is about 277.0462372911.

The spelling of 21264578 in words is "twenty-one million, two hundred sixty-four thousand, five hundred seventy-eight".