21999000 has 64 divisors (see below), whose sum is σ = 68646240. Its totient is φ = 5865600.

The previous prime is 21998993. The next prime is 21999007. The reversal of 21999000 is 99912.

It is an interprime number because it is at equal distance from previous prime (21998993) and next prime (21999007).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21999007) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 667 + ... + 6666.

Almost surely, 2^21999000 is an apocalyptic number.

21999000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21999000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34323120).

21999000 is an abundant number, since it is smaller than the sum of its proper divisors (46647240).

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

21999000 is a wasteful number, since it uses less digits than its factorization.

21999000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7357 (or 7343 counting only the distinct ones).

The product of its (nonzero) digits is 1458, while the sum is 30.

The square root of 21999000 is about 4690.3091582539. The cubic root of 21999000 is about 280.1996874871.

The spelling of 21999000 in words is "twenty-one million, nine hundred ninety-nine thousand".