21394731 has 4 divisors (see below), whose sum is σ = 28526312. Its totient is φ = 14263152.

The previous prime is 21394697. The next prime is 21394733. The reversal of 21394731 is 13749312.

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

It is not a de Polignac number, because 21394731 - 2⁷ = 21394603 is a prime.

It is a super-2 number, since 2×21394731² = 915469029124722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21394733) 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, 3565786 + ... + 3565791.

It is an arithmetic number, because the mean of its divisors is an integer number (7131578).

Almost surely, 2^21394731 is an apocalyptic number.

21394731 is a deficient number, since it is larger than the sum of its proper divisors (7131581).

21394731 is an equidigital number, since it uses as much as digits as its factorization.

21394731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7131580.

The product of its digits is 4536, while the sum is 30.

The square root of 21394731 is about 4625.4438705923. The cubic root of 21394731 is about 277.6103221765.

The spelling of 21394731 in words is "twenty-one million, three hundred ninety-four thousand, seven hundred thirty-one".