21397570 has 8 divisors (see below), whose sum is σ = 38515644. Its totient is φ = 8559024.

The previous prime is 21397559. The next prime is 21397573. The reversal of 21397570 is 7579312.

It can be written as a sum of positive squares in 2 ways, for example, as 20784481 + 613089 = 4559^2 + 783^2 .

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 (21397573) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1069869 + ... + 1069888.

Almost surely, 2^21397570 is an apocalyptic number.

21397570 is a deficient number, since it is larger than the sum of its proper divisors (17118074).

21397570 is a wasteful number, since it uses less digits than its factorization.

21397570 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2139764.

The product of its (nonzero) digits is 13230, while the sum is 34.

The square root of 21397570 is about 4625.7507498783. The cubic root of 21397570 is about 277.6226009138.

The spelling of 21397570 in words is "twenty-one million, three hundred ninety-seven thousand, five hundred seventy".