21487019 has 4 divisors (see below), whose sum is σ = 21496296. Its totient is φ = 21477744.

The previous prime is 21487009. The next prime is 21487051. The reversal of 21487019 is 91078412.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21487019 is a prime.

It is a super-2 number, since 2×21487019² = 923383971012722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21487009) 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, 2087 + ... + 6879.

It is an arithmetic number, because the mean of its divisors is an integer number (5374074).

Almost surely, 2^21487019 is an apocalyptic number.

21487019 is a deficient number, since it is larger than the sum of its proper divisors (9277).

21487019 is an equidigital number, since it uses as much as digits as its factorization.

21487019 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9276.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 21487019 is about 4635.4092591701. The cubic root of 21487019 is about 278.0089148841.

The spelling of 21487019 in words is "twenty-one million, four hundred eighty-seven thousand, nineteen".