21273751 has 4 divisors (see below), whose sum is σ = 21726432. Its totient is φ = 20821072.

The previous prime is 21273739. The next prime is 21273761. The reversal of 21273751 is 15737212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21273751 is a prime.

It is a super-2 number, since 2×21273751² = 905144963220002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21273761) 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, 226270 + ... + 226363.

It is an arithmetic number, because the mean of its divisors is an integer number (5431608).

Almost surely, 2^21273751 is an apocalyptic number.

21273751 is a deficient number, since it is larger than the sum of its proper divisors (452681).

21273751 is an equidigital number, since it uses as much as digits as its factorization.

21273751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 452680.

The product of its digits is 2940, while the sum is 28.

The square root of 21273751 is about 4612.3476668612. The cubic root of 21273751 is about 277.0860684726.

The spelling of 21273751 in words is "twenty-one million, two hundred seventy-three thousand, seven hundred fifty-one".