21391854 has 16 divisors (see below), whose sum is σ = 46673280. Its totient is φ = 6482360.

The previous prime is 21391849. The next prime is 21391871. The reversal of 21391854 is 45819312.

It is a super-2 number, since 2×21391854² = 915222835114632, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a Curzon number.

It is a plaindrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161994 + ... + 162125.

It is an arithmetic number, because the mean of its divisors is an integer number (2917080).

Almost surely, 2^21391854 is an apocalyptic number.

21391854 is an abundant number, since it is smaller than the sum of its proper divisors (25281426).

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

21391854 is a wasteful number, since it uses less digits than its factorization.

21391854 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324135.

The product of its digits is 8640, while the sum is 33.

The square root of 21391854 is about 4625.1328629565. The cubic root of 21391854 is about 277.5978779802.

It can be divided in two parts, 2139 and 1854, that added together give a palindrome (3993).

The spelling of 21391854 in words is "twenty-one million, three hundred ninety-one thousand, eight hundred fifty-four".