21315946 has 4 divisors (see below), whose sum is σ = 31973922. Its totient is φ = 10657972.

The previous prime is 21315923. The next prime is 21315947. The reversal of 21315946 is 64951312.

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., 16524225 + 4791721 = 4065^2 + 2189^2 .

It is not an unprimeable number, because it can be changed into a prime (21315947) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5328985 + ... + 5328988.

Almost surely, 2^21315946 is an apocalyptic number.

21315946 is a deficient number, since it is larger than the sum of its proper divisors (10657976).

21315946 is a wasteful number, since it uses less digits than its factorization.

21315946 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10657975.

The product of its digits is 6480, while the sum is 31.

The square root of 21315946 is about 4616.9195357944. The cubic root of 21315946 is about 277.2691411131.

It can be divided in two parts, 2131594 and 6, that added together give a square (2131600 = 1460²).

The spelling of 21315946 in words is "twenty-one million, three hundred fifteen thousand, nine hundred forty-six".