21493511 has 4 divisors (see below), whose sum is σ = 23146872. Its totient is φ = 19840152.

The previous prime is 21493489. The next prime is 21493517. The reversal of 21493511 is 11539412.

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 21493511 - 2²² = 17299207 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21493517) 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, 826661 + ... + 826686.

It is an arithmetic number, because the mean of its divisors is an integer number (5786718).

Almost surely, 2^21493511 is an apocalyptic number.

21493511 is a deficient number, since it is larger than the sum of its proper divisors (1653361).

21493511 is a wasteful number, since it uses less digits than its factorization.

21493511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1653360.

The product of its digits is 1080, while the sum is 26.

The square root of 21493511 is about 4636.1094680777. The cubic root of 21493511 is about 278.0369108901.

The spelling of 21493511 in words is "twenty-one million, four hundred ninety-three thousand, five hundred eleven".