21154391 has 16 divisors (see below), whose sum is σ = 22982400. Its totient is φ = 19410048.

The previous prime is 21154387. The next prime is 21154403. The reversal of 21154391 is 19345112.

It is a cyclic number.

It is not a de Polignac number, because 21154391 - 2² = 21154387 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21154391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21154381) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 126590 + ... + 126756.

It is an arithmetic number, because the mean of its divisors is an integer number (1436400).

Almost surely, 2^21154391 is an apocalyptic number.

21154391 is a deficient number, since it is larger than the sum of its proper divisors (1828009).

21154391 is a wasteful number, since it uses less digits than its factorization.

21154391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 358.

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

The square root of 21154391 is about 4599.3902856792. The cubic root of 21154391 is about 276.5668834208.

The spelling of 21154391 in words is "twenty-one million, one hundred fifty-four thousand, three hundred ninety-one".