21971898 has 40 divisors (see below), whose sum is σ = 53025588. Its totient is φ = 6759936.

The previous prime is 21971897. The next prime is 21971899. The reversal of 21971898 is 89817912.

It is an interprime number because it is at equal distance from previous prime (21971897) and next prime (21971899).

It can be written as a sum of positive squares in 2 ways, for example, as 21650409 + 321489 = 4653^2 + 567^2 .

It is not an unprimeable number, because it can be changed into a prime (21971891) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3111 + ... + 7322.

Almost surely, 2^21971898 is an apocalyptic number.

21971898 is an abundant number, since it is smaller than the sum of its proper divisors (31053690).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21971898 is a wasteful number, since it uses less digits than its factorization.

21971898 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10460 (or 10451 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 21971898 is about 4687.4191193022. The cubic root of 21971898 is about 280.0845747915.

It can be divided in two parts, 2197 and 1898, that added together give a triangular number (4095 = T₉₀).

The spelling of 21971898 in words is "twenty-one million, nine hundred seventy-one thousand, eight hundred ninety-eight".