21881749 has 4 divisors (see below), whose sum is σ = 23033440. Its totient is φ = 20730060.

The previous prime is 21881723. The next prime is 21881767. The reversal of 21881749 is 94718812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21881749 - 2⁷ = 21881621 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 (21881789) 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, 575817 + ... + 575854.

It is an arithmetic number, because the mean of its divisors is an integer number (5758360).

Almost surely, 2^21881749 is an apocalyptic number.

It is an amenable number.

21881749 is a deficient number, since it is larger than the sum of its proper divisors (1151691).

21881749 is a wasteful number, since it uses less digits than its factorization.

21881749 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1151690.

The product of its digits is 32256, while the sum is 40.

The square root of 21881749 is about 4677.7931762745. The cubic root of 21881749 is about 279.7009945883.

The spelling of 21881749 in words is "twenty-one million, eight hundred eighty-one thousand, seven hundred forty-nine".