21425618 has 4 divisors (see below), whose sum is σ = 32138430. Its totient is φ = 10712808.

The previous prime is 21425603. The next prime is 21425639. The reversal of 21425618 is 81652412.

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., 20638849 + 786769 = 4543^2 + 887^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5356403 + ... + 5356406.

Almost surely, 2^21425618 is an apocalyptic number.

21425618 is a deficient number, since it is larger than the sum of its proper divisors (10712812).

21425618 is a wasteful number, since it uses less digits than its factorization.

21425618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10712811.

The product of its digits is 3840, while the sum is 29.

The square root of 21425618 is about 4628.7814811244. The cubic root of 21425618 is about 277.7438508016.

The spelling of 21425618 in words is "twenty-one million, four hundred twenty-five thousand, six hundred eighteen".