21873457 has 4 divisors (see below), whose sum is σ = 22030960. Its totient is φ = 21715956.

The previous prime is 21873451. The next prime is 21873497. The reversal of 21873457 is 75437812.

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 a de Polignac number, because none of the positive numbers 2^k-21873457 is a prime.

It is a super-2 number, since 2×21873457² = 956896242261698, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21873451) 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, 78543 + ... + 78820.

It is an arithmetic number, because the mean of its divisors is an integer number (5507740).

Almost surely, 2^21873457 is an apocalyptic number.

It is an amenable number.

21873457 is a deficient number, since it is larger than the sum of its proper divisors (157503).

21873457 is a wasteful number, since it uses less digits than its factorization.

21873457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157502.

The product of its digits is 47040, while the sum is 37.

The square root of 21873457 is about 4676.9067769200. The cubic root of 21873457 is about 279.6656596056.

It can be divided in two parts, 218734 and 57, that added together give a triangular number (218791 = T₆₆₁).

The spelling of 21873457 in words is "twenty-one million, eight hundred seventy-three thousand, four hundred fifty-seven".