21861967 has 4 divisors (see below), whose sum is σ = 22161520. Its totient is φ = 21562416.

The previous prime is 21861893. The next prime is 21861971. The reversal of 21861967 is 76916812.

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

It is a cyclic number.

It is not a de Polignac number, because 21861967 - 2⁷ = 21861839 is a prime.

It is a super-2 number, since 2×21861967² = 955891202218178, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21861977) 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, 149667 + ... + 149812.

It is an arithmetic number, because the mean of its divisors is an integer number (5540380).

Almost surely, 2^21861967 is an apocalyptic number.

21861967 is a deficient number, since it is larger than the sum of its proper divisors (299553).

21861967 is an equidigital number, since it uses as much as digits as its factorization.

21861967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 299552.

The product of its digits is 36288, while the sum is 40.

The square root of 21861967 is about 4675.6782395712. The cubic root of 21861967 is about 279.6166821128.

The spelling of 21861967 in words is "twenty-one million, eight hundred sixty-one thousand, nine hundred sixty-seven".