21403651 has 4 divisors (see below), whose sum is σ = 21515904. Its totient is φ = 21291400.

The previous prime is 21403643. The next prime is 21403667. The reversal of 21403651 is 15630412.

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 21403651 - 2³ = 21403643 is a prime.

It is a super-2 number, since 2×21403651² = 916232552259602, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21403621) 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, 55840 + ... + 56221.

It is an arithmetic number, because the mean of its divisors is an integer number (5378976).

Almost surely, 2^21403651 is an apocalyptic number.

21403651 is a deficient number, since it is larger than the sum of its proper divisors (112253).

21403651 is a wasteful number, since it uses less digits than its factorization.

21403651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112252.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21403651 is about 4626.4080018952. The cubic root of 21403651 is about 277.6488977182.

The spelling of 21403651 in words is "twenty-one million, four hundred three thousand, six hundred fifty-one".