21361898 has 4 divisors (see below), whose sum is σ = 32042850. Its totient is φ = 10680948.

The previous prime is 21361897. The next prime is 21361919. The reversal of 21361898 is 89816312.

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., 12439729 + 8922169 = 3527^2 + 2987^2 .

It is not an unprimeable number, because it can be changed into a prime (21361897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5340473 + ... + 5340476.

Almost surely, 2^21361898 is an apocalyptic number.

21361898 is a deficient number, since it is larger than the sum of its proper divisors (10680952).

21361898 is a wasteful number, since it uses less digits than its factorization.

21361898 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10680951.

The product of its digits is 20736, while the sum is 38.

The square root of 21361898 is about 4621.8933349873. The cubic root of 21361898 is about 277.4682397436.

It can be divided in two parts, 2136 and 1898, that multiplied together give a triangular number (4054128 = T₂₈₄₇).

The spelling of 21361898 in words is "twenty-one million, three hundred sixty-one thousand, eight hundred ninety-eight".