21379731 has 8 divisors (see below), whose sum is σ = 30006720. Its totient is φ = 13502952.

The previous prime is 21379703. The next prime is 21379741. The reversal of 21379731 is 13797312.

It is a happy number.

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

It is not a de Polignac number, because 21379731 - 2¹⁴ = 21363347 is a prime.

It is a super-2 number, since 2×21379731² = 914185795264722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21379692 and 21379701.

It is not an unprimeable number, because it can be changed into a prime (21379741) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 187485 + ... + 187598.

It is an arithmetic number, because the mean of its divisors is an integer number (3750840).

Almost surely, 2^21379731 is an apocalyptic number.

21379731 is a deficient number, since it is larger than the sum of its proper divisors (8626989).

21379731 is a wasteful number, since it uses less digits than its factorization.

21379731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 375105.

The product of its digits is 7938, while the sum is 33.

The square root of 21379731 is about 4623.8221202810. The cubic root of 21379731 is about 277.5454288096.

The spelling of 21379731 in words is "twenty-one million, three hundred seventy-nine thousand, seven hundred thirty-one".