21673251 has 20 divisors (see below), whose sum is σ = 33070752. Its totient is φ = 14138928.

The previous prime is 21673241. The next prime is 21673259. The reversal of 21673251 is 15237612.

It is a happy number.

It is not a de Polignac number, because 21673251 - 2⁵ = 21673219 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21673259) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 961 + ... + 6653.

Almost surely, 2^21673251 is an apocalyptic number.

21673251 is a deficient number, since it is larger than the sum of its proper divisors (11397501).

21673251 is an equidigital number, since it uses as much as digits as its factorization.

21673251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5752 (or 5743 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21673251 is about 4655.4538983863. The cubic root of 21673251 is about 278.8097905754.

The spelling of 21673251 in words is "twenty-one million, six hundred seventy-three thousand, two hundred fifty-one".