21570493 has 4 divisors (see below), whose sum is σ = 24652000. Its totient is φ = 18488988.

The previous prime is 21570473. The next prime is 21570499. The reversal of 21570493 is 39407512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21570493 - 2⁹ = 21569981 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21570499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1540743 + ... + 1540756.

It is an arithmetic number, because the mean of its divisors is an integer number (6163000).

Almost surely, 2^21570493 is an apocalyptic number.

It is an amenable number.

21570493 is a deficient number, since it is larger than the sum of its proper divisors (3081507).

21570493 is an equidigital number, since it uses as much as digits as its factorization.

21570493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3081506.

The product of its (nonzero) digits is 7560, while the sum is 31.

The square root of 21570493 is about 4644.4044828159. The cubic root of 21570493 is about 278.3684580036.

The spelling of 21570493 in words is "twenty-one million, five hundred seventy thousand, four hundred ninety-three".