21519731 has 4 divisors (see below), whose sum is σ = 21600000. Its totient is φ = 21439464.

The previous prime is 21519727. The next prime is 21519791. The reversal of 21519731 is 13791512.

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

It is a cyclic number.

It is not a de Polignac number, because 21519731 - 2² = 21519727 is a prime.

It is a super-2 number, since 2×21519731² = 926197644624722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21519694 and 21519703.

It is not an unprimeable number, because it can be changed into a prime (21519721) 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, 39731 + ... + 40268.

It is an arithmetic number, because the mean of its divisors is an integer number (5400000).

Almost surely, 2^21519731 is an apocalyptic number.

21519731 is a deficient number, since it is larger than the sum of its proper divisors (80269).

21519731 is an equidigital number, since it uses as much as digits as its factorization.

21519731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80268.

The product of its digits is 1890, while the sum is 29.

The square root of 21519731 is about 4638.9364082729. The cubic root of 21519731 is about 278.1499243076.

The spelling of 21519731 in words is "twenty-one million, five hundred nineteen thousand, seven hundred thirty-one".