21372751 has 4 divisors (see below), whose sum is σ = 21382600. Its totient is φ = 21362904.

The previous prime is 21372737. The next prime is 21372761. The reversal of 21372751 is 15727312.

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 not a de Polignac number, because 21372751 - 2⁵ = 21372719 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 (21372761) 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, 81 + ... + 6538.

It is an arithmetic number, because the mean of its divisors is an integer number (5345650).

Almost surely, 2^21372751 is an apocalyptic number.

21372751 is a deficient number, since it is larger than the sum of its proper divisors (9849).

21372751 is an equidigital number, since it uses as much as digits as its factorization.

21372751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9848.

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

The square root of 21372751 is about 4623.0672718445. The cubic root of 21372751 is about 277.5152214143.

The spelling of 21372751 in words is "twenty-one million, three hundred seventy-two thousand, seven hundred fifty-one".