21881407 has 4 divisors (see below), whose sum is σ = 23033080. Its totient is φ = 20729736.

The previous prime is 21881383. The next prime is 21881459. The reversal of 21881407 is 70418812.

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

It is a cyclic number.

It is not a de Polignac number, because 21881407 - 2¹⁵ = 21848639 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 (21881477) 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, 575808 + ... + 575845.

It is an arithmetic number, because the mean of its divisors is an integer number (5758270).

Almost surely, 2^21881407 is an apocalyptic number.

21881407 is a deficient number, since it is larger than the sum of its proper divisors (1151673).

21881407 is a wasteful number, since it uses less digits than its factorization.

21881407 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1151672.

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 21881407 is about 4677.7566204325. The cubic root of 21881407 is about 279.6995373886.

The spelling of 21881407 in words is "twenty-one million, eight hundred eighty-one thousand, four hundred seven".