21015970 has 16 divisors (see below), whose sum is σ = 38348280. Its totient is φ = 8290944.

The previous prime is 21015947. The next prime is 21015971. The reversal of 21015970 is 7951012.

It can be written as a sum of positive squares in 4 ways, for example, as 20061441 + 954529 = 4479^2 + 977^2 .

It is not an unprimeable number, because it can be changed into a prime (21015971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13665 + ... + 15124.

Almost surely, 2^21015970 is an apocalyptic number.

21015970 is a deficient number, since it is larger than the sum of its proper divisors (17332310).

21015970 is a wasteful number, since it uses less digits than its factorization.

21015970 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28869.

The product of its (nonzero) digits is 630, while the sum is 25.

The square root of 21015970 is about 4584.3178336586. The cubic root of 21015970 is about 275.9623364555.

Adding to 21015970 its reverse (7951012), we get a palindrome (28966982).

The spelling of 21015970 in words is "twenty-one million, fifteen thousand, nine hundred seventy".