21019431 has 4 divisors (see below), whose sum is σ = 28025912. Its totient is φ = 14012952.

The previous prime is 21019409. The next prime is 21019459. The reversal of 21019431 is 13491012.

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

It is not a de Polignac number, because 21019431 - 2¹⁰ = 21018407 is a prime.

It is a super-2 number, since 2×21019431² = 883632959127522, 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 = 21019398 and 21019407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019231) 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, 3503236 + ... + 3503241.

It is an arithmetic number, because the mean of its divisors is an integer number (7006478).

Almost surely, 2^21019431 is an apocalyptic number.

21019431 is a deficient number, since it is larger than the sum of its proper divisors (7006481).

21019431 is an equidigital number, since it uses as much as digits as its factorization.

21019431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7006480.

The product of its (nonzero) digits is 216, while the sum is 21.

The square root of 21019431 is about 4584.6953006716. The cubic root of 21019431 is about 275.9774845107.

The spelling of 21019431 in words is "twenty-one million, nineteen thousand, four hundred thirty-one".