21891270 has 32 divisors (see below), whose sum is σ = 54236160. Its totient is φ = 5649120.

The previous prime is 21891269. The next prime is 21891281. The reversal of 21891270 is 7219812.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10840 + ... + 12699.

It is an arithmetic number, because the mean of its divisors is an integer number (1694880).

Almost surely, 2^21891270 is an apocalyptic number.

21891270 is an abundant number, since it is smaller than the sum of its proper divisors (32344890).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21891270 is a wasteful number, since it uses less digits than its factorization.

21891270 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23580.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21891270 is about 4678.8107463329. The cubic root of 21891270 is about 279.7415557431.

The spelling of 21891270 in words is "twenty-one million, eight hundred ninety-one thousand, two hundred seventy".