21290397 has 8 divisors (see below), whose sum is σ = 29303040. Its totient is φ = 13735680.

The previous prime is 21290371. The next prime is 21290411. The reversal of 21290397 is 79309212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21290397 - 2⁸ = 21290141 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21290597) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 114372 + ... + 114557.

It is an arithmetic number, because the mean of its divisors is an integer number (3662880).

Almost surely, 2^21290397 is an apocalyptic number.

It is an amenable number.

21290397 is a deficient number, since it is larger than the sum of its proper divisors (8012643).

21290397 is a wasteful number, since it uses less digits than its factorization.

21290397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 228963.

The product of its (nonzero) digits is 6804, while the sum is 33.

The square root of 21290397 is about 4614.1518180485. The cubic root of 21290397 is about 277.1583198307.

It can be divided in two parts, 212 and 90397, that added together give a palindrome (90609).

The spelling of 21290397 in words is "twenty-one million, two hundred ninety thousand, three hundred ninety-seven".