21291370 has 16 divisors (see below), whose sum is σ = 38465928. Its totient is φ = 8485120.

The previous prime is 21291367. The next prime is 21291373. The reversal of 21291370 is 7319212.

It is an interprime number because it is at equal distance from previous prime (21291367) and next prime (21291373).

It can be written as a sum of positive squares in 4 ways, for example, as 11909401 + 9381969 = 3451^2 + 3063^2 .

It is not an unprimeable number, because it can be changed into a prime (21291373) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 979 + ... + 6598.

Almost surely, 2^21291370 is an apocalyptic number.

21291370 is a deficient number, since it is larger than the sum of its proper divisors (17174558).

21291370 is a wasteful number, since it uses less digits than its factorization.

21291370 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7865.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21291370 is about 4614.2572533399. The cubic root of 21291370 is about 277.1625419367.

The spelling of 21291370 in words is "twenty-one million, two hundred ninety-one thousand, three hundred seventy".