21042772 has 6 divisors (see below), whose sum is σ = 36824858. Its totient is φ = 10521384.

The previous prime is 21042739. The next prime is 21042803. The reversal of 21042772 is 27724012.

It can be written as a sum of positive squares in only one way, i.e., 18627856 + 2414916 = 4316^2 + 1554^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2630343 + ... + 2630350.

Almost surely, 2^21042772 is an apocalyptic number.

It is an amenable number.

21042772 is a deficient number, since it is larger than the sum of its proper divisors (15782086).

21042772 is a wasteful number, since it uses less digits than its factorization.

21042772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5260697 (or 5260695 counting only the distinct ones).

The product of its (nonzero) digits is 1568, while the sum is 25.

The square root of 21042772 is about 4587.2401288792. The cubic root of 21042772 is about 276.0795996692.

Adding to 21042772 its reverse (27724012), we get a palindrome (48766784).

The spelling of 21042772 in words is "twenty-one million, forty-two thousand, seven hundred seventy-two".