21361493 has 4 divisors (see below), whose sum is σ = 21557580. Its totient is φ = 21165408.

The previous prime is 21361489. The next prime is 21361519. The reversal of 21361493 is 39416312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12229009 + 9132484 = 3497^2 + 3022^2 .

It is a cyclic number.

It is not a de Polignac number, because 21361493 - 2² = 21361489 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 (21361423) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 97880 + ... + 98097.

It is an arithmetic number, because the mean of its divisors is an integer number (5389395).

Almost surely, 2^21361493 is an apocalyptic number.

It is an amenable number.

21361493 is a deficient number, since it is larger than the sum of its proper divisors (196087).

21361493 is a wasteful number, since it uses less digits than its factorization.

21361493 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196086.

The product of its digits is 3888, while the sum is 29.

The square root of 21361493 is about 4621.8495215660. The cubic root of 21361493 is about 277.4664862268.

The spelling of 21361493 in words is "twenty-one million, three hundred sixty-one thousand, four hundred ninety-three".