21870351 has 8 divisors (see below), whose sum is σ = 32400560. Its totient is φ = 14580216.

The previous prime is 21870337. The next prime is 21870353. The reversal of 21870351 is 15307812.

It is not a de Polignac number, because 21870351 - 2⁷ = 21870223 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 810013 = 21870351 / (2 + 1 + 8 + 7 + 0 + 3 + 5 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21870353) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 404980 + ... + 405033.

It is an arithmetic number, because the mean of its divisors is an integer number (4050070).

Almost surely, 2^21870351 is an apocalyptic number.

21870351 is a deficient number, since it is larger than the sum of its proper divisors (10530209).

21870351 is an equidigital number, since it uses as much as digits as its factorization.

21870351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 810022 (or 810016 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 21870351 is about 4676.5747080529. The cubic root of 21870351 is about 279.6524216028.

The spelling of 21870351 in words is "twenty-one million, eight hundred seventy thousand, three hundred fifty-one".