21387970 has 8 divisors (see below), whose sum is σ = 38498364. Its totient is φ = 8555184.

The previous prime is 21387959. The next prime is 21387973. The reversal of 21387970 is 7978312.

It can be written as a sum of positive squares in 2 ways, for example, as 21150801 + 237169 = 4599^2 + 487^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21387973) 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 3 ways as a sum of consecutive naturals, for example, 1069389 + ... + 1069408.

Almost surely, 2^21387970 is an apocalyptic number.

21387970 is a deficient number, since it is larger than the sum of its proper divisors (17110394).

21387970 is a wasteful number, since it uses less digits than its factorization.

21387970 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2138804.

The product of its (nonzero) digits is 21168, while the sum is 37.

The square root of 21387970 is about 4624.7129640660. The cubic root of 21387970 is about 277.5810763288.

The spelling of 21387970 in words is "twenty-one million, three hundred eighty-seven thousand, nine hundred seventy".