21439477 has 4 divisors (see below), whose sum is σ = 21680460. Its totient is φ = 21198496.

The previous prime is 21439471. The next prime is 21439489. The reversal of 21439477 is 77493412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4866436 + 16573041 = 2206^2 + 4071^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21439477 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 (21439471) 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, 120358 + ... + 120535.

It is an arithmetic number, because the mean of its divisors is an integer number (5420115).

Almost surely, 2^21439477 is an apocalyptic number.

It is an amenable number.

21439477 is a deficient number, since it is larger than the sum of its proper divisors (240983).

21439477 is an equidigital number, since it uses as much as digits as its factorization.

21439477 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240982.

The product of its digits is 42336, while the sum is 37.

The square root of 21439477 is about 4630.2782853734. The cubic root of 21439477 is about 277.8037234017.

The spelling of 21439477 in words is "twenty-one million, four hundred thirty-nine thousand, four hundred seventy-seven".