21006746 has 4 divisors (see below), whose sum is σ = 31510122. Its totient is φ = 10503372.

The previous prime is 21006743. The next prime is 21006779. The reversal of 21006746 is 64760012.

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., 20151121 + 855625 = 4489^2 + 925^2 .

It is not an unprimeable number, because it can be changed into a prime (21006743) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5251685 + ... + 5251688.

Almost surely, 2^21006746 is an apocalyptic number.

21006746 is a deficient number, since it is larger than the sum of its proper divisors (10503376).

21006746 is a wasteful number, since it uses less digits than its factorization.

21006746 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10503375.

The product of its (nonzero) digits is 2016, while the sum is 26.

The square root of 21006746 is about 4583.3116847974. The cubic root of 21006746 is about 275.9219568602.

Adding to 21006746 its reverse (64760012), we get a palindrome (85766758).

The spelling of 21006746 in words is "twenty-one million, six thousand, seven hundred forty-six".