21523402 has 4 divisors (see below), whose sum is σ = 32285106. Its totient is φ = 10761700.

The previous prime is 21523399. The next prime is 21523417. The reversal of 21523402 is 20432512.

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

It can be written as a sum of positive squares in only one way, i.e., 20711601 + 811801 = 4551^2 + 901^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21523402.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5380849 + ... + 5380852.

Almost surely, 2^21523402 is an apocalyptic number.

21523402 is a deficient number, since it is larger than the sum of its proper divisors (10761704).

21523402 is a wasteful number, since it uses less digits than its factorization.

21523402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10761703.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21523402 is about 4639.3320639937. The cubic root of 21523402 is about 278.1657397208.

Adding to 21523402 its reverse (20432512), we get a palindrome (41955914).

The spelling of 21523402 in words is "twenty-one million, five hundred twenty-three thousand, four hundred two".